《水经注·卷二》
《神仙传》说：封君达，陇西人，他以水银炼丹服食，到了一百岁时，看来还像三十左右的样子。他常常骑着青牛，所以号为青牛道士。
《神仙传》曰：封君达，陇西人，服炼水银，年百岁，视之如年三十许，骑青牛，故号青牛道士。
"Biography of Immortals" said: Feng Junda, a native of Longxi, took mercury alchemy and ate it. At the age of 100, he still looked like he was about 30. He often rode a green cow, so he was called the Green Cow Taoist.