Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s5.34

v2.c12.s5.34

We find in Atharva Jyotiṣa, discussion of the shadow cast by a gnomon, which proves* that the gnomon was known to us before our science of astronomy came in contact with that of the Westerners. The Pañca Siddhāntikā contains a chapter on instruments, which is not quite intelligible ; still it appears that many of the instruments described by Brahmagupta and others were in use in those times. Āryabhaṭa I has not described any instruments at all, but has mentioned a globe as described above. He has, in addition, stated that a globe should be so prepared for finding time that it will automatically rotate with the help of mercury, oil, or water.** Take a wheel. Fix in it somewhat hollow spokes half filled with mercury, with their ends sealed. The wheel will then rotate automatically. Brahmagupta and Bhāskarācārya have mentioned one such automatic instrument. From the globe instrument of Āryabhaṭa described above and from the references in the Pañca Siddhāntikā to some wonders occurring automatically by means of the instruments, it appears that at the time of Varāhamihira there existed such instruments and some other kinds of ‘swayam waha’ i.e., automatically working instruments. Varāhamihira and Āryabhaṭa have not described the process of construction. Brahmagupta also has described, in addition to the above instruments, some other wonders happening automatically, but has not described their processes.