In Chang Chu's Hua Yang Guo Chi (Historical Geography of Sichuan) of 347, not only rivers, trade routes, and various tribes were described, but it also wrote of a 'Ba Jun Tu Jing' ('Map of Sichuan'), which had been made much earlier in 150. The Shui Jing (Waterways Classic) was written anonymously in the 3rd century during the Three Kingdoms era (attributed often to Guo Pu), and gave a description of some 137 rivers found throughout China. In the 6th century, the book was expanded to forty times its original size by the geographers Li Daoyuan, given the new title of Shui Jing Zhu (The Waterways Classic Commented). In later periods of the Song dynasty (960–1279) and Ming dynasty (1368–1644), there were much more systematic and professional approaches to geographic literature. The Song dynasty poet, scholar, and government official Fan Chengda (1126–1193) wrote the geographical treatise known as the Gui Hai Yu Heng Chi. It focused primarily on the topography of the land, along with the agricultural, economic and commercial products of each region in China's southern provinces. The polymath Chinese scientist Shen Kuo (1031–1095) devoted a significant amount of his written work to geography, as well as a hypothesis of land formation (geomorphology) due to the evidence of marine fossils found far inland, along with bamboo fossils found underground in a region far from where bamboo was suitable to grow. The 14th-century Yuan dynasty geographer Na-xin wrote a treatise of archeological topography of all the regions north of the Yellow River, in his book He Shuo Fang Gu Ji. The Ming dynasty geographer Xu Xiake (1587–1641) traveled throughout the provinces of China (often on foot) to write his enormous geographical and topographical treatise, documenting various details of his travels, such as the locations of small gorges, or mineral beds such as mica schists. Xu's work was largely systematic, providing accurate details of measurement, and his work (translated later by Ding Wenjiang) read more like a 20th-century field surveyor than an early 17th-century scholar. The Chinese were also concerned with documenting geographical information of foreign regions far outside of China. Although Chinese had been writing of civilizations of the Middle East, India, and Central Asia since the traveler Zhang Qian (2nd century BC), later Chinese would provide more concrete and valid information on the topography and geographical aspects of foreign regions. The Tang dynasty (618–907) Chinese diplomat Wang Xuance traveled