Yong-le: Year 13, Month 4, Day 23
31 May 1415
The Jiao-zhi Provincial Administration Commission had previously advised of the situation in respect of official salt in the region and had requested that regulations be set down enabling merchants to be summoned and allowing salt to be sold for gold, silver and copper cash. At this time, the Ministry of Revenue proposed that for each liang of gold, 30 yin of salt be supplied and that for each liang of silver or 2,500 (Alt: 250) wen of copper cash, three yin of salt be supplied. This was approved.
Zhong-yang Yan-jiu yuan Ming Shi-lu, volume 13, page 1847