When the Ming founder Hongwu came upon the mechanical devices housed in the Yuan dynasty's palace at Khanbaliq – such as fountains with balls dancing on their jets, self-operating tiger automata, dragon-headed devices that spouted mists of perfume, and mechanical clocks in the tradition of Yi Xing (683–727) and Su Song (1020–1101) – he associated all of them with the decadence of Mongol rule and had them destroyed. This was described in full length by the Divisional Director of the Ministry of Works, Xiao Xun, who also carefully preserved details on the architecture and layout of the Yuan dynasty palace. Later, European Jesuits such as Matteo Ricci and Nicolas Trigault would briefly mention indigenous Chinese clockworks that featured drive wheels. However, both Ricci and Trigault were quick to point out that 16th-century European clockworks were far more advanced than the common time keeping devices in China, which they listed as water clocks, incense clocks, and "other instruments ... with wheels rotated by sand as if by water" (Chinese: ). Chinese records – namely the "Yuan Shi" – describe the 'five-wheeled sand clock', a mechanism pioneered by Zhan Xiyuan (fl. 1360–80) which featured the scoop wheel of Su Song's earlier astronomical clock and a stationary dial face over which a pointer circulated, similar to European models of the time. This sand-driven wheel clock was improved upon by Zhou Shuxue (fl. 1530–58) who added a fourth large gear wheel, changed gear ratios, and widened the orifice for collecting sand grains since he criticized the earlier model for clogging up too often.