《新唐书·列传·卷一百四十二》
有条康干河，如砍一段松树丢在河里，三年后即化为石，颜色苍致，但木节纹理依旧，即俗称康干石的。
有川曰康干河，断松投之，三年辄化为石，色苍致，然节理犹在，世谓康干石者。
There is a Kanggan River, if a pine tree is cut and thrown into the river, it will become a stone in three years, with a pale color, but the wood fiber texture is still there. It is commonly called Kanggan Stone.