Jantar Mantar

The largest example is the equinoctial sundial belonging to Jaipur's assembly of instruments, consisting of a gigantic triangular gnomon with the hypotenuse parallel to the Earth's axis. On either side of the gnomon is a quadrant of a circle, parallel to the plane of the equator. The instrument can be used with an accuracy of about 20 seconds by a skilled observer to determine the time of day, and the declination of the Sun and the other heavenly bodies. It is the world's largest stone sundial, and is known as the Samrat Yantra.The Jaipur Jantar Mantar is a UNESCO World Heritage Site.

History

In the early 18th century, Sawai Jai Singh of Jaipur constructed five Jantar Mantar in total, in New Delhi, Jaipur, Ujjain, Mathura and Varanasi; they were completed between 1724 and 1735.

The observatory at Mathura and the fort that protected it were destroyed before 1857.

As part of Jantar Mantar there were many instruments like Samrat Yantra, Jai Prakash Yantra, Disha Yantra, Rama Yantra, Chakra Yantra, Rashiwalya Yantra, Dingash Yantra and Utaansh Yantra. The primary purpose of the instruments was to compile astronomical tables and to predict the times and movements of the Sun, Moon and Planets.