Zhang Gongzui

In the next few days, Zhang Xu began to purchase large quantities of saltpeter.
He opened a shop in the city to buy saltpeter.
The price of one tael of silver per catty was enough to drive the people of Shuofang City crazy.
Anyway, winter has already arrived in Shuobei, and most people don't have much to do, so they just go around scraping saltpeter off the walls all day long.
Places such as latrines and animal sheds where saltpeter is easily precipitated have become gold mines in...