Sui-Wai Cheung's study of the institutional history of copper coins in the Ming dynasty reveals how emperors and statesmen perceived and used the copper coins at their disposal. In this process, he uncovers the reality of the Sons of Heaven, showing that although Ming emperors seemed to have unlimited power, they could not afford the upkeep on their palace. In this revealing history of Ming China, Cheung argues that especially after the breakdown of the household registration system, the aim of the Ming coinage system was to create a new source of income in order to maintain the emperor's domain in Beijing.