Gengshen waishi 庚申外史

The chronicle Gengshen waishi 庚申外史 is an account of the events that took place during the reign of Emperor Yuan Shundi 元順帝 (r. 1333-1368/1370) of the Yuan dynasty 元 (1279-1368). It is also known under the title Gengshen dashi ji 庚申大事記 "Records of important events of the Gengshen reign", the long title is Gengshendi waishi wenjian lu 庚申帝外史聞見錄 "Evidential unofficial history of the Gengshen Emperor".

Emperor Yuan Shundi was born in a year with the cyclical characters gengshen, hence the name. Quan Heng 權衡, author of this 2-juan long chronicle, was not an official at the Yuan court but dwelled somewhere in the Yellow River Plain and thus became witness of the events during the last decades of the Yuan dynasty when the central government lost its grip on the provinces.

The Gengshen waishi gives a detailed account of the factional strives of the mighty Mongolian warlords like Köke Temür 擴廓帖木兒 (c. 1315-1375), El Temür 燕鐵木兒 (1285-1333) and Toγtaγa 脫脫 (1314-1355). The material contained in Quan Heng's book served as basis for the respective chapters in the official dynastic history of the Yuan period, the Yuanshi 元史.