The money Europe took 600 years to copy

In the Chinese region of Sichuan, people paid with iron coins so worthless that doing the shopping meant hauling kilos of metal. Around the year 1000, merchants began leaving their iron on deposit and paying with the paper receipts instead. In 1024, the Song dynasty government took over the idea and issued the jiaozi: the first official banknotes in history.

When Marco Polo reached China in the 13th century, he watched Emperor Kublai Khan pay entire armies with stamped paper and told the story in wonder on his return: the Great Khan, he said, seemed to have mastered alchemy. Many in Europe took him for a teller of tall tales.

Europe's first banknote didn't arrive until 1661, in Sweden. It took Europe over six centuries to believe an idea that was already routine in China: value lies not in the paper, but in who signs it.