Jantar Mantar, in Jaipur, is the most famous of five observatories built by
Sawai Jai Singh in India. The Jantar mantar is a mis-prounounciation of
Sanskrit word Yantra Mantra. It was built to check the astronomical
observation at Jaipur. The Jantar Mantar at Jaipur was conceived as a quest
for discovering the mysteries of the Cosmos .The sun dial of Jantar mantar
is one of the major tourist attraction
Sawai Jai Singh sent his ambassadors to all parts of the world before
starting the construction of this observatory. The ambassadors returned with
many manuals on astronomy containing cutting-edge technological information.
One of these manuals was a copy of La Hire's "Tables". The king
ordered the observatory to be built according to the details contained in
this manual.
The Observatory

Jai Singh had the choice of constructing the observatory either with metal
instruments or masonry instruments. The metal instruments, constructed
according to the texts of the Islamic school of astronomy, did not measure
up to Jai Singh's expectations. He discarded them in favor of the
instruments of stone and masonry that he himself designed.
Instruments in the Observatory
» Samrat Yantra : Samrat Yantra consists of a massive triangle
with a curved structure on both sides.
» Ram Yantra : It is an instrument used to indicate the
altitude and the azimuth or declination of celestial bodies.
» Jai Prakash Yantra : It is used to find out the positions of
the celestial bodies during days and nights. It is a two hemispherical bowl
structure, which represents the celestial sphere and there is a vertical rod
in the center.