Wu Collection, Lower Volume Radical: Cave (xué) 窞 Kangxi Strokes: 13 Page 866, Entry 32 Tang Rhymes (Tangyun), Collected Rhymes (Jiyun), Dictionary of Rhymes (Yunhui), and Correct Rhymes (Zhengyun) state the pronunciation is dan (third tone). According to the Explaining Graphs and Analyzing Characters (Shuowen): A small pit inside a larger pit. Another definition is to enter from the side. Book of Changes (Yijing), Hexagram of Water (Kan): Practicing the water hexagram and entering into the pit (dan). The Commentary (Zhu) states: It is the deepest part at the bottom of the pit, into which one enters. Ma Rong, Rhapsody on the Long Flute (Changdi Fu): The pit (dan) is rocky and deep. Additionally, according to Collected Rhymes (Jiyun): Pronounced lan (rising tone), with the same meaning. Sometimes written in a variant form (kan).