Rajasthan: The Jantar Mantar in Jaipur


In our first day of touring Jaipur, after visiting the Amber Fort, (post here) we were taken to a fascinating outdoor park containing various structures that functioned as “instruments” to measure the movements of the sun, stars, and planets.

The Jantar Mantar, an astronomical observatory in the middle of the city of Jaipur, is very interesting from several points of view: as an early advanced astronomical observatory, as an artifact of a society that wants to act during “auspicious times,” and as a relic from and memorial to an amazing man, Maharaja Jai Singh II.

Why was it built?

There are several answers to this straightforward question. It was built due to the abiding interest of Maharaja Jai Singh II in astronomy. It was built so that scientists of that time could use it to make more careful observations of the movements of the sun and heavens and create accurate star charts. It was built so that an Indian intellectual could prove his merit by designing new instruments for astronomical measurement. It was built so that a Maharaja of the Sun God could show his link with the heavens. It was built so that the Maharaja and his government could schedule events properly with accurate measurements of the planets so that the best days could be accurately forecasted for big events.

Its predecessor, the Jantar Mantar in Delhi, was also built by Jai Singh II (after receiving permission from the Mughal Emperor Muhammad Shah), this time with the express purpose of correcting existing information. At that time India was influenced by both Muslim and Hindu astrology, whose charts of the planets did not agree. From a paper published by the Math Department, University of Singapore:

It is intriguing to note that the construction of the magnificent Delhi observatory can be traced back to a dispute. The controversial debate over certain planetary positions took place in 1719 at the Delhi public courtroom of the Red Fort. The Emperor Muhammad Shah was to embark on a long expedition and an auspicious date had already been fixed. However, some astrologers determined certain discrepancies over planetary positions which, at that time, were believed to influence life on Earth.

The heated disagreement between the Hindu and Muslim astrologers failed to reach conciliation based on their own astrological observations. Witnessing this, Jai Singh bore the sentiments that the reason leading to the disagreement was largely due to inaccurate astrological tables.

The idea of building an observatory dawned on Jai Singh who then requested Emperor Muhammad Shah to allow him to undertake the responsibility of correcting the astrological tables. Seeing that Jai Singh was himself a learned man in astronomy and mathematics, the Emperor readily granted this request.

It is likely that the Emperor was willing for a more political reason: his plan for building the Delhi observatory, and subsequent ones, was tempered in the fact that the India of that era was a land saturated with superstitious beliefs and strong mythical influences. Important events such as religious ceremonies and sacrificial rites were to be strictly carried out on auspicious days. As such, with the longevity of the Empire said to depend on sacrificial rites and ceremonies, accuracy of planetary positions became a topmost priority.

Who Built It?

It was built by Maharaja Jai Singh II, as a part of the royal palace grounds in the new “Pink City” of Jaipur. Jai Singh II, by all accounts, was an extraordinary person. Again from the University of Singapore Math Department paper:

Jai Singh entered the political scene at the young age of eleven to succeed his father Maharaja Bishan Singh in 1699 A.D. as the ruler of Amber (also known as “Amer”), a few years after Aurangzeb’s death. Jai Singh was deemed a highly intellectual individual way beyond his age. He even won the praises of emperor Aurangzeb when he was first presented to the Delhi court at the age of seven in 1696 A.D.

Legend has it that at that time, Jai Singh had gone to pay his respects to the emperor who held his hands and asked, “How do you expect to be powerful with your hands tied?”
With sheer confidence and composure, Jai Singh replied, “When a bridegroom takes his bride’s hand, he pledges to protect her for life. With your Majesty taking my hand, what for do I need power?”

Emperor Aurangzeb was deeply impressed by such an intelligent reply and bestowed upon Jai Singh the title sawai, meaning one-and-a-quarter of an average man in worth.

Even today in Jaipur, they fly the Jaipur flag, and another smaller one beneath it, signifying Emperor Aurangzeb’s evaluation of Jai Singh II as one-and-a-quarter man.

Jai Singh was well educated by his father, receiving the best possible education from the best teachers and scholars in the fields of art, science, philosophy and military affairs. Jai Singh was extremely interested in arts and science, especially astronomy. He studied the works of Ptolemy, Euclid, and Persian astronomers, and showed the greatest interest in Arabic-Persian astronomy. However, he remained a firm follower of the geocentric system of Indian tradition and of Ptolemy.

These interests in astronomy are not too surprising. In India at that time, celestial phenomena were often associated with gods and the sacred Truth. As a result, people firmly believed that secrets were revealed by the gods in the movement and position of every star up in the sky. So in Jai Singh’s case, it was not unusual that astronomy aroused such strong passion in him. Especially since his family traced their lineage back to the Sun God, it may be concluded that Jai Singh felt every need to be in touch with his “ancestral origin.” This was based on a strong religious belief yet rational scientific approach.

Jai Singh became one of the important allies that Emperor Muhammad Shah depended on. Emperor Muhammad Shah recognized him as a man of talent, and gave him important duties in his empire. As his influence grew, there became a rising demand to initiate the construction of a new city to resolve the problem of limited resources in his sovereign state of Amber. So he started building Jaipur City. In the town planning process, Jai Singh decided to put theoretical architectural design into reality. He adopted the architectural style from the sacred texts of the Shilpa Shastra, the source of the Indian ideas of Vaastu, (the Indian equivalent of Chinese system of Feng Shui).

Again from the University of Singapore Math Department paper:

Jai Singh’s interest in a holistic urban format for his city of Jaipur stemmed from his desire to display his powers and portray himself as a divine figure, particularly Indra, ruler of the universe. Jaipur was an excellent opportunity to put forth this self-proclaimed image. Therefore, details of the layout and building of every section of the city were planned in such a way that it played a significant role in implying this close relationship he had with the celestial world.

So Jaipur is laid out on a grand scale, with Sun and Moon Gates on the east and west of the city. Its broad streets are laid out in a grid, and are said to be the first divided streets in the world, with separate lanes for each direction of traffic.

The most obvious element is the 108-foot-wide axial road that runs along from east (the Sun Gate) to west (the Moon Gate) — the pathway of the sun. The “Pole Star Gate” (Druv Pol) is dictated by the North Celestial star. The Pole Star is ritually interpreted as a gift from the gods to keep the kingdom in a stable state of affairs. These three cardinal points form the fundamental triangulation of Hindu Kingship and are expressed through the architecture of Jaipur. The city plan of Jaipur is interpreted widely as a square mandala.

About the Name, Yantra

Yantra is a Sanskrit word meaning “instrument” or “machine.” It refers to geometric figures that can be used to bind the Supreme Principle to a given spot, so that this place becomes a representation of the entire manifest universe.

Again from the University of Singapore Math Department paper:

The instruments’ construction was based heavily on Hindu tradition. The significance of mandalas was illustrated through the architecture of Jai Singh’s building program. The stone blocks that serve as bases for instruments such as the Ram Yantra have a similar orientation to the bricks in the Vedic fire altar.

The instruments of Jai Singh all bear the word “Yantra” towards the end of the name. This has a lot to do with the much-emphasized Mandala. The Yantras … represent the Truth determining the lives of Man and even the Gods. They encompass the secret meaning of the sacred truth, precisely the message that Jai Singh planned to convey: that he was the truth bearer, the quintessence of the divine, the ultimate King of the universe.

So naming these instruments all Yantras, emphasizes that Jai Singh II built the Jantar Mantar to show his special link with the heavens, and reinforce his position as the current ruler from the Sun God.

The Jaipur Jantar Mantar

The observatory consists of fourteen major geometric devices for measuring time, predicting eclipses, tracking stars’ location as the earth orbits around the sun, ascertaining the declinations of planets, and determining the celestial altitudes and related ephemerides (star charts). Each is a fixed and “focused” tool. For example, the largest instrument, the Samrat Yantra, is 90 feet (27 m) high, its shadow carefully plotted to tell the time of day to within two seconds. Its face is angled at 27 degrees, the latitude of Jaipur.

We wandered through the Jantar Mantar, as usual with no organized plan, just going from one instrument to another, as they attracted our eyes.

Laghu (Small) Samrat Yantra (Equinoctial Sundial)

  • It measures time, a sundial.
  • Invented and designed by Jai Singh II.

It is a big sundial, though it is called the “Small” Samrat Yantra. It is accurate within about 15 seconds. Probably this was built before the large one, discussed below.

The small Samrat Yantra is one of the first things you will notice entering the grounds.


Stairs ascend the gnomon, the part of a sundial that casts the shadow.


Below, a man is reading the current time. We were told by our guide that they have a table of adjustments to use to correct the reading for the change in the sun’s position in the sky over the span of the year. Today he adds eleven minutes to the actual reading.


Broad arcs spread out on both sides of the gnomon. These are the scales, used to read the time.


It is currently faced with marble, with time lines marked closely on it. The original construction of the gnomons and scales was made of plaster, making it extremely hard to obtain accurate readings. Accuracy was improved in later years when these instruments were refinished, using marble for the scales.


Next are two matching instruments, one facing north and the other south.

Nadivalaya Yantra (Equinoctial Dial)

  • Helps in determining the time.
  • Only northern part (Uttari Gola) built originally, the southern part was added before the reign of Maharaja Pratap Singh, when the whole building was rebuilt (1771).
  • Both instruments are needed, since as the sun moves north and south during the year, only one or the other receives direct sunlight.

Here is a sign explaining this Yantra.


You can see the size of the instrument.


A pin inserted in the center of the instrument is the gnomon, and the shadow gives the reading.


Jai Prakash Yantras (Hemispherical Instrument)

  • These are twin hemispherical bowl instruments. Each one is a reflection of sky above.
  • Constructed under the supervision of Maharaja Sawai Jai Singh II (before 1743).
  • Invented and designed by Jai Singh II, one of three.

The names translates to “Light of Jai.” I think the gnomon is a ring of metal, hung in the center of the instrument on wires.

Explanation of this instrument, from the University of Singapore Math Department paper:

The fundamental principle upon which the Jai Prakash Yantras were designed was that a hemisphere recessed in the ground would inversely represent the heavens above the observer. Appropriate scales such as the azimuthal, altitudinal, declination and right ascension lines; and important celestial reference markers such as the zenith and the North Celestial Pole, were inscribed onto the hemisphere to allow observations of the sun and stars.

It is hard to see the size of the instrument in these photos. It is 50 or 50 feet wide.

If you look carefully you can see the ring, suspended on wires. It is easier to see the sire in this photo.


The other end of the instrument.


You can see the gnomon, the ring, in the left of this photo, and its shadow to the right.


It was used, apparently, by an observer climbing down within the instrument, observing the sky from specific locations within the instrument. The photo below is also from the University of Singapore Math Department paper. The photo gives a good sense of the scale of the instrument.


Etched into the instrument are various coordinates, the lines shown below. The shadow of the gnomon is seen as well. If we knew what all the lines meant, we could tell what the reading of the instrument is right now.


And in some places there are scales, too.


For precise measurements.


Vrihat Samrat Yantra – The Supreme Instrument (Equinoctial Sundial)

  • This is a large sundial that can give the time to an accuracy of 2 seconds.
  • Planned around 1732, completed around 1735.
  • Designed by Jai Singh II.

Versions of the Samrat Yantra can be found at all the observatories built by Jai Singh II, and other archeo-astronomical sites around the world. It is not fundamentally different from the time telling technique used by the basic sundial. The sun’s shadow moves as the day passes form dawn to dusk. The geometry of this design with its large size has made it the most accurate sun dial on the planet.


Samrat Yantra is the world’s largest sundial. Its gnomon rises 27 meters (about 90 feet) above its base, and the marble-faced quadrants create an arc that spans a 15-meter radial (about 50 feet) on each side. So the shadow of the sun moves about 4 meters per hour, or 6 cm. per minute. With fine divisions and markings on the scale, a 2-second accuracy is theoretically possible.

To solve the inaccuracy introduced by the partial shadow of the sun, the penumbra, which spans a width of about 10 centimeters on this scale, special measures had to be taken. With every 2 seconds being 0.2 centimeters on the scale, the penumbra makes an accurate measurement difficult. Accordingly they used a small lead instrument or sidestick. By running this sidestick up or down the length of the ramp and locating it based on the day of the year, it became possible to determine the time precisely, within the design limits of the instrument. The resourceful usage of this sidestick negated appreciably the effects of shade diffraction, the penumbra, making the Samrat Yantra effectively the most precise sundial available, anywhere. I think this is still the case, since a larger sundial has never been built.

This shows this massive instrument.


A sign providing explanation.


One “wing,”or quadrant, curves out to the left of the gnomon.


The photo below shows the wing to the right and the stairs that go all the way to the top. At the top is a small structure, a chatri (literally “parasol”) whose sides are oriented in the four main directions and ribs in the minor ones. Typical of Rajput architecture, the axes symbolize the major axes of the universe. The chatri was used as a platform for determining wind direction, announcing eclipses and onset of monsoons.


It is a long way up.


You can see the markings on the scale.


This is a scale model of the instrument.


Rasivalaya Yantra (Ecliptic Dial)

  • Measures the celestial latitude and longitude of zodiacs.

These were constructed before 1750’s, though not a part of initial lists of instruments from Maharaja Jai Singh’s time.


This instrument consists of a number of small devices, similar in design to the sundials, but all with different orientations. A description, from http://www.khagolmandal.com:

Rasivalayas were also invented by Jai Singh. The Rasivalayas are a set of 12 instruments based on the principle of the Samrat, which measure the latitude and longitude of a celestial object. A particular Rasivalaya instrument becomes operative when the first point of the sign of the zodiac it represents approaches the meridian. At that moment, its ‘gnomon’ points toward the pole of the ecliptic and its quadrants become parallel to the plane of the ecliptic. Because there are 12 signs of the zodiac, there are 12 Rasivalayas, representing each sign. These were built only at Jaipur.


A list of planets. I assume this list is related to these instruments.


You can see the central gnomon, and the two wings. Since these are for the planets, I assume they must have been used at night. So I wonder how they were used, since there is no shadow from the planet at night?


As you can see, these fascinate photographers.


Another view of one of the instruments.


The Rasivalaya Yantra with the Vrihat Samrat Yantra in the background.


Great Rama Yantra (Cylindrical Instrument)

  • This measures the local co-ordinates of altitude and azimuth of celestial objects, particularly the sun.
  • This is the third instrument that was designed by Sai Singh II.

Azimuth is an astronomical term. The diagram below show this better than I can explain it.  (from Wikimedia commons):

The azimuth is the angle formed between a reference direction (North) and a line from the observer to a point of interest projected on the same plane as the reference direction.

The Rama Yantra was used to measure the position of both the sun and stars. Unlike the Jai Prakash Yantra, which used a ring as its gnomon, the Rama Yantra used a stick in the center of a flat, elevated, circular, scaled surface as its gnomon. Also, it used only one coordinate measurement system, instead of two. It was based on the horizon and zenith system.


Informative sign.


The Rama Yantra is best described as a large hollow drum with its top end uncovered and a pole erected in the center. The pole is the gnomon.


A sign designating a repair of the Rama Yantra, made more than 100 years ago.


Another view of the Rama Yantra.


Krantivritta II (Measures Celestial Latitude & Longitude)

  • Measurement of celestial latitudes and longitudes.
  • Built in 1901-1902 by Garrett, to demonstrate the function of the Krantivritta Yantra as the original Yantra was left incomplete.

The sign gives a good description of its functioning.


You can see the stone base and the metal wheels that are used in this instrument.


Frontal view.


Yantra Raj (Astrolabe)

  • Used for measuring ascendant (rising star in astrology, the point of the zodiac that rises above the eastern horizon at any moment) altitude, time, position of the sun and that of some other celestial objects.
  • No record in original plans, though Tieffenthaler (1750’s) mentions two large metal astrolabes suspended on iron rings.
  • Due to the interest of Jai Singh II in Astrolabes, I think this was planned by him.

Descriptive sign.


It looks like a big brass gong.


Except it is marked with carefully laid out lines, inscribed in its surface, and a big hole, for the sighting tube, I think.


Chakra Yantra (Measures Declination of a Celestial Body)

  • Measures declination – distance from north or south of the celestial equator.

Informative sign.


These look like big brass wheels.


Kapala Yantra (Hemispherical Dial)

  • Used for measuring the ascendant and zodiacs.
  • Constructed under the supervision of Maharaja Jai Singh II (before 1743).

This is similar to the Jai Prakash Yantra, using a bowl to depict the heavens above, with a ring suspended on wires as its gnomon.


Digamsa Yantra (Azimuth Circle)

  • Determines the azimuth of a celestial object.
  • Constructed under the supervision of Jai Singh II (before 1743)

Descriptive sign.


Concentric rings make up this Yantra. A string was used for measurement.


A small metal sun dial. This uses the same basic design as the two Samrat Yantras.


View of the grounds. The Vrihat Samrat Yantra is so huge that it dominates all these views.



This was an amazing place. I had never heard of it, nor of Maharaja Jai Singh II and his deep interest in astronomy. It is also interesting to me that while Europe was developing and using small metal instruments to determine latitude and longitude (essential to ocean navigation), Jai Singh II went the other way, making massive stone instruments.


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