The Great Rama Yantra

The Rama Yantra is a series vertical columns that support an equal number of horizontal slabs in two identical stone structures . The readings from these determine the celestial arc from horizon to zenith as well as the altitude of the sun. Again the scale of the devices helped ensure their accuracy. The use of the device is quite ingenuous--simply insert an iron rod into the center, and read the numbers off the incremental markings on the horizontal fans, the vertical columns, and the ring on the top. The fans or spokes on the two Rama Yantra instruments  are complimentary. so that if the shadow falls between the spokes on one of the instruments, it can be read on the other. The photo to the left shows the larger of the two Rama Yantra instruments, while the photo to the right shows the interior of one of the Rama Yantra instruments, with the iron rod centered between the fans or spokes.