Cheng-hua: Year 17, Month 7, Day 26
21 Aug 1481
The Mt. Na-geng police office was established in Yun-nan and a native official was selected as the police officer to guard it. Previously, the two subprefectures of Ning-yuan and Jian-shui were both under the jurisdiction of Lin-an Prefecture. Later, Ning-yuan fell under Annam's jurisdiction. The "black-leg" Bai-yi (黑腳百夷) came across the border year after year attacking and harassing the villages and stockades of Che-li. It was commanded that the defence officials map the borders and advise. At this time, the Censor-in-Chief Wu Cheng, grand coordinator of Yun-nan, and others advised: "The two mountains of Shi-yai and Pai-gan form the border between the two subprefectures. The "black-leg" Bai-yi generally cross the border through there to engage in disorder. We should block this route at a strategic point to prevent them from coming and going. As to the water route, the border is marked by the course of the river from Man-wang Stockade. Formerly, merchants took their goods through here when going to Lian-hua Rapids to trade with the the Jiao people. It is appropriate that a police office be established there with a native official in charge, in order to facilitate matters." The memorial was sent to the Ministry of War which requested approval for the memorialized proposal. It was approved.
Zhong-yang Yan-jiu yuan Ming Shi-lu, volume 48, page 3766