This statement accurately describes the information presented in "The Mongols" by J. M. Roberts. Paper money was first developed in China during the Song dynasty in the 1100s. During the Mongol Yuan Dynasty, the Mongols adopted this practice and issued their own money. They also implemented this system in Persia. The Mongols introduced the practice to Marco Polo (who visited Kublai Khan's court), thus introducing it to Europe.
They are not foolish because they gave what was most precious to them to each other. It is wise because they give up something they treasure for the one they love.