《明史·志·卷五十八》
四年，设置易州山厂，命令工部侍郎督办，指派北直、山东、山西民夫转运，而后军都督府交纳银召集商人办理如故。
四年置易州山厂，命工部侍郎督之，佥北直、山东、山西民夫转运，而后府输银召商如故。
In the fourth year, the Yizhou Mountain Factory was established, and a minister of public works was ordered to supervise the project and command porters from northern Zhili, Shandong, and Shanxi to transport the supplies. The Duty-bound Rear Army Command raised silver to pay merchants to handle it as before.