Gu Yanwu
The essay format didn't become prevalent as a standard essay in the civil service examination until early Ming dynasty (1368–1644), when the composition of the essay was clearly specified. In the seventeenth century, Gu Yanwu stated that this form of essay-writing became standardized precisely during the 15th century, when the eight parts of the essay were determined. The term "eight-legged essay" formally appeared during the early years of the Chenghua Emperor's reign (1464–1487) for the first time. Then, it started to be required in civil service examinations in the 1480s.