Jai Prakash Yantra
The Jai Prakash Yantra consists of two sunken hemispheres that map out the heavens. This instrument is believed by some historians to have been invented by Sawai Jai Singh II himself to verify the accuracy of all others in the observatory. It is in fact a larger version of the Chakra Yantra, located nearby. Apparently the small size of the Chakra Yantra made precise determination as to the location of the stars difficult. In addition to its larger size, the other innovation of the Jai Prakash Yantra was the fact that there were openings in the hemispheres, which could be accessed from a lower level. This allowed observers to get a much closer look at where the shadows fell on these hemispheres.