Hong-zhi: Year 2, Month 5, Day 17
15 Jun 1489
Ruan Qing and other yi artisans from the Embroidered-Uniform Guard were originally Annam persons. During the Yong-le reign (1403-24), as they were able to manufacture cannons, short guns (短鎗) and rockets (神箭), and embroider dragon robes, they were appointed as military artisans with a monthly salary of one shi of rice. Later, regulations were issued reducing this to five dou. At this time, Qing and the others stated that they were yi persons and had no family to support them. It was thus commanded that their salary be again raised to one shi of rice.
Zhong-yang Yan-jiu yuan Ming Shi-lu, volume 52, page 585