Rotary Winnowing Fan

Timeline

1. 100–200Central Plains region · Central PlainsLiu Xi of the Eastern Han wrote in Shiming: 'Dui, dui, means to crush; a pestle is used to crush wheat, and the wind fan is similar.' Wang Zhen's Nongshu later cited that by the Han dynasty devices using a rotating impeller to blow air for winnowing grain already existed, one of the earliest documentary clues to the winnowing fan.
2. c. 801–900Jiangnan and Sichuan Basin agricultural regions · Sichuan BasinDuring the Tang agricultural boom, rice and wheat producing areas widely adopted hand-cranked winnowing fans for post-harvest winnowing; the 'wind fan' imagery in poems by Liu Yuxi, Bai Juyi and others corroborates agricultural records, showing the technology was an everyday farm tool by the 9th century.
3. 1313Fuzhou, Jiangxi · JiangxiWang Zhen's Nongshu - Illustrated Manual of Farm Tools details the structure and use of the 'wind fan': an upright wooden frame with a rotatable impeller; grain is fed from above into the airflow, chaff is blown away and plump kernels fall for collection; this account summarizes the mature form of the winnowing fan since the Tang and influenced later agricultural books.