Surya Siddhanta
The Surya Siddhanta (IAST: Sūrya Siddhānta; lit. 'Sun Treatise') is a Sanskrit treatise in Indian astronomy, attributed to Lāṭadeva, a student of Aryabhatta I, and dated to somewhere between the end of the 4th and 9th centuries, and comprises fourteen chapters. The Surya Siddhanta describes the author's rules, within a geocentric model, to calculate the motions of the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn, along with his estimate of their diameters, and the circumference of their assumed circular orbits around the Earth.