Tian-qi: Year 1, Month 12, Day 19
30 Jan 1622
Previously, Li Zhi-zao, vice minister in the Court of Imperial Entertainment, had made a proposal, saying: "In order to defend the cities with firearms, we must obtain Western Ocean large cannons (西洋大銃) and train troops in their use." The Han-lin official Xu Guang-qi thus ordered that Commandant Sun Xue-shi to proceed to Guang-dong and, in Xiang Shan Bay (香山嶴), purchase four cannons. At this time they arrived in the capital. It was ordered that he proceed again to Guang-dong to obtain "red yi" bronze cannons (紅夷銅銃) and to recruit and send to the capital some yi merchants familiar with the manufacture and firing of the cannons.
Zhong-yang Yan-jiu yuan Ming Shi-lu, volume 126, page 867