Zheng Xuan
The "Zhouli" commentary of Zheng Xuan (127–200) glosses "fusui" as "yangsui". The sub-commentary of Jia Gongyan 賈公彦 says the "fusui" is called "yangsui" because it starts a fire by means of the "jīng" 精 "spirit; essence" of the "taiyang" "great "yang"; sun".