Jantar Mantar Statistics
Jantar Mantar is constructed entirely of stone because Jai Singh hated metal observatories. It has six astrological instruments, namely: Samrat Yantra, Jai Prakash Yantra, Niyata Yantra, Ram Yantra, Misra Yantra and Agra Yantra. The one in Delhi is today the largest and most preserved observatory amongst others, though the one is Jaipur is built on a larger scale. Till date the instruments have predicted accurately with a 10 % error margin.

Coming Into Being
Jantar Mantar was built in 1724 under the orders of emperor Muhammad Shah to observe the Sun, Moon and the Stars and compile astronomical tables and charts. Jai Singh invented brass instruments for calculating astronomical values and later replaced them with instruments made of brick, lime and clay. The one in Mathura no longer exists now as it was destroyed by a government contractor Jyoti Prasad little before 1857 AD who bought it for want of materials.

Interesting Fact
Jantar Mantar in Delhi was used only for seven years which explains its still excellent condition. Today it is more famous for the peaceful protests held just outside the boundary wall.

The Instruments
The instruments can be called the brick and mortar blow-ups of the metal astronomical instruments used in studying the heavenly bodies. The observatory has fourteen statistical instruments for measuring time, predicting eclipses and to ascertain other astronomical events. Amongst all the instruments, the Sundial usually attracts the maximum attention of people, which tells the time to an accuracy of about two seconds in local time. Another famous Yantra is the Niyta Yantra which can show about accurate time for meridians of Greenwich, Zurich, Notkey (Japan), and Serichew (Pacific Ocean), acting as an ancient world clock.