the Book of Jin that Pei Xiu made a critical study of ancient texts in order to update the naming conventions of geographic locations described in old texts. His maps – drawn on rolls of silk – were presented to Emperor Wu, who preserved them in the imperial court's archives. Pei Xiu's maps have since been lost, decayed or destroyed. Yet the oldest existing terrain maps from China date to the fourth century BCE, found in a Qin tomb in present-day Gansu in 1986. Han dynasty maps from the second century BCE were found earlier in the 1973 excavation of Mawangdui. In 1697, the Qing dynasty cartographer Hu Wei (胡渭) reconstructed Pei Xiu's maps in his Yugong Zhuizhui (禹貢錐指, A Few Points on the Vast Subject of the Yu Gong). Modern scholars have also used Pei Xiu's writing to reproduce his works, and historians such as Herrmann have compared Pei Xiu to other great ancient cartographers such as the Greek cartographer Ptolemy (83–161). Written works Pei Xiu wrote a preface to his maps with essential background information regarding older maps in China. He also provided a great deal of criticism about the existing maps from the Han dynasty in his time. Later Chinese ideas about the quality of maps made during the Han dynasty and before stem from the assessment given by Pei Xiu, which was not a positive one. Pei Xiu noted that the extant Han maps at his disposal were of little use since they featured too many inaccuracies and exaggerations in measured distance between locations. However, the Qin maps and Mawangdui maps of the Han dynasty discovered by modern archaeologists were far superior in quality than those examined and criticised by Pei Xiu. It was not until the 20th century that Pei Xiu's third century assessment of earlier maps' dismal quality would be overturned and disproven. The makers of the Han maps were familiar with the use of scale, while the Qin map makers had pinpointed the course of rivers with some accuracy. What these earlier maps did not feature was topographical elevation, which Pei Xiu would outline with his six principles of cartography. Pei Xiu's preface describes geographers in the Xia, Shang and Zhou dynasties, although the earliest known geographical work was the Yu Gong chapter of the Shu Ji or Book of Documents, compiled in the fifth century BCE during the mid Zhou period. Pei