Records of the Imperial Title-Conferring Envoys to Ryukyu (Shi Liu Qiu Lu)

In 1561 (the 40th year of Emperor Jiajing’s reign of the Ming Dynasty), Guo Rulin, an imperial title-conferring envoy from the Ming court to Ryukyu and Li Jichun, Guo’s deputy, described in Records of the Imperial Title-Conferring Envoys to Ryukyu (Shi Liu Qiu Lu), “The first day of May on the lunar calendar, we passed Diaoyu Yu. And on the third day of May on the lunar calendar, we arrived at Chi Yu, which separates China and Ryukyu. The following day, we saw Kume Mountain.” This passage implies that Chi Yu (also known as Chiwei Yu) was considered the border between China and Ryukyu.