"What is the sound of one hand clapping?" is a koan from this school of Mahayana Buddhism
[DOC] [TLE] What are the major differences between Tibetan Buddhism and the ... [PAR] Having practiced under both Soto Zen and now under Nyingma Tibetan 
buddhisms, here is my ... Zen Buddhism: How do Soto and Rinzai approaches to 
koans differ?