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

In 1663 (the 2nd year of the reign of Emperor Kangxi of the Qing Dynasty), Zhang Xueli was sent to Ryukyu as an imperial title-conferring envoy from the Qing court. His Records of the Imperial Title-Conferring Envoys to Ryukyu (Shi Liu Qiu Ji) recorded his voyage to Ryukyu in the form of a journal: “The color of the water becomes different, dark blue. The boatman told me we were entering the ocean. Instantly, a white line spans from the south to north. The boatman told me the line is the border line separating China from foreign land.”