For the post-Vedic period we have, in addition to the results of internal evidence, a few landmarks of general chronological importance in the visits of foreigners. The earliest date of this kind is that of the invasion of India by Alexander in 326 B.C. This was followed by the sojourn in India of various Greeks, of whom the most notable was Megasthenes. He resided for some years about 300 B.C. at the court of Pataliputra (the modern Patna), and has left a valuable though fragmentary account of the contemporary state of Indian society. Many centuries later India was visited by three Chinese Buddhist pilgrims, Fa Hian (399 A.D.), Hiouen Thsang (630-645), and I Tsing (671-695). The records of their travels, which have been preserved, and are all now translated into English, shed much light on the social conditions, the religious thought, and the Buddhist antiquities of India in their day. Some general and specific facts about Indian literature also can be gathered from them. Hiouen Thsang especially supplies some important statements about contemporary Sanskrit poets. It is not till his time that we can say of any Sanskrit writer that he was alive in any particular year, excepting only the three Indian astronomers, whose exact dates in the fifth and sixth centuries have been recorded by themselves. It was only the information supplied by the two earlier Chinese writers that made possible the greatest archæological discovery of the present century in India, that of the site of Buddha's birthplace, Kapila-vastu, identified in December 1896. At the close of our period we have the very valuable account of the country at the time of the Muhammadan conquest by the Arabic author Alberuni, who wrote his India in 1030 A.D.