Tofu (bean curd), a popular East Asian food now becoming a global food, originated in China in the early imperial period.
The artisanal method of making tofu has not changed much: grinding soybeans, filtering and boiling soy milk, coagulating it, and pressing it into shape. It is still widely used today.
The soybeans first need to be grounded into fine powder. The soybean powder is then mixed with water. After stirring, the liquid is filtered to obtain soy milk. They soy milk would be boiled and then coagulated by adding a coagulant (such as gypsum or vinegar). The coagulated tofu would be pressed into a solid block and then cut into desired sizes.
Source: Pan Wenlong (潘文龍) and Gong Wei (龔為), Old Trades of Jiangsu: A Glimpse《江蘇老行當百業寫真》, Phoenix Education Publishing Company, 2018. Permission to use the photo has been obtained.