An important mathematician and astronomer in medieval India, Bhascara Acharya (1114–85) wrote treatises on arithmetic, algebra, geometry and astronomy. He is also believed to have been head of the astronomical observatory at Ujjain, which was the leading centre of mathematical sciences in India. Forming part of his Sanskrit magnum opus Siddhānta Shiromani, the present work is his treatise on algebra. It was first published in English in 1813 after being translated from a Persian text by the East India Company civil servant Edward Strachey (1774–1832). The topics covered include operations involving positive and negative numbers, surds and zero, as well as algebraic, simultaneous and indeterminate equations. Strachey also appends useful notes made by the orientalist Samuel Davis (1760–1819). Of enduring interest in the history of mathematics, this was notably the first work to acknowledge that a positive number has two square roots.