Money and Lending in Ancient China: Copper Talks

The anticipated listing and the unexpected suspension put the microloan business of Alibaba's fintech arm Ant Group in the media spotlight. Chinese people seem to have long impressed the world for their preference for saving. Their enthusiasm for borrowing is apparently a new phenomenon. But did ancient Chinese borrow? If they did, how?  Why was the "square hole the big brother" so important for more than 2,000 years in China? How can ancient rich people keep 10 million copper coins in their house?