Gu Yanwu
The scholar Gu Yanwu of the early Qing dynasty (1644–1912) estimated that the previous Ming dynasty had to employ 47,004 full-time laborers recruited by the "lijia" corvée system in order to maintain the entire canal system. It is known that 121,500 soldiers and officers were needed simply to operate the 11,775 government grain barges in the mid-15th century.