The astrolabe, a kind of celestial map engraved upon apair of 7-foot wide metal disks, was one of the most sophisticated astronomical instruments of its time in the western world. Raja Sawai Sing II managed to procure one, which he named Raj Yantra, "The King of all Instruments." He wrote two volumes on the principles and utility of the device, which became one of his fondest possessions. The disk to the right in the photograph is inscribed with a map of the zodiac, while the one to the left is a map of the planets.