"[Xu Xiake 徐霞客, 1587-1641] ... was the best known of those who traveled inside China in the later empire. Between the years 1607 and 1640 he went on seventeen trips culminating in a four-year exploration of Guangxi, Guizhou, and Yunnan. He left behind lengthy diaries of his travels, amounting to 404,000 characters, of which the greater part is devoted to his last great exploration in the southwest. Xu not only climbed all the sacred mountains of China, but also explored the sources of major rivers and made geographical and geological investigations despite the many hardships along the way...." Cf. Wilkinson, Chinese History, a Manual, pp. 168-169.
Biography of Xu Xiake: Eminent Chinese of the Ch'ing Period, pp. 314-316.