evidence: How does this relate to the present dispute over the Senkaku/Diaoyu islands? Since 1970 the People’s Republic of China, Taiwan and Japan have all put forward bold sovereignty claims over the islands, which are equidistant from Taiwan and the southwestern tip of the Ryukyus. According to Chinese sources the first mention of the Senkaku/Diaoyu islands is in a 15th-century document now held at the Bodleian Library in Oxford. Early sources tended to mention only the islands’ location on the voyage to the Ryukyus from China, but by the 17th century Chinese sources clearly named the maritime boundary between the Senkaku/Diaoyu islands and the Ryukyus as the Heishuigou (‘Black Water Trench’), an area of high turbulence which we now know marks the edge of the continental shelf. In 1720 Xu Baoguang, the deputy Chinese ambassador sent to confer the royal title upon the Ryukyuan king, collaborated with the local literati to compile the travelogue Zhongshan Chuanxin lu (Record of the Mission to Chusan), which demarcated the westernmost border of the Ryukyuan kingdom at Kume-jima south of the Heishuigou Trench.