The Surya Siddhanta 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 5th centuries by most modern scholars, 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. The text is known from a 15th-century CE palm-leaf manuscript, and several newer manuscripts. It was composed or revised probably c. 800 CE from an earlier text also called the Surya Siddhanta. The Surya Siddhanta text is composed of verses made up of two lines, each broken into two halves, or pãds, of eight syllables each.