Final answer:
Hakuin Ekaku is credited with a famous Japanese Zen koan, which asks, "What is the sound of one hand?" It is a riddle intended to transcend logical thinking and is said to take years for students to understand and answer as they seek enlightenment.
Step-by-step explanation:
Hakuin Ekaku, an influential figure in the Rinzai school of Japanese Zen Buddhism, is credited with creating many Zen koans, which are paradoxical anecdotes or riddles used to demonstrate the inadequacy of logical reasoning and to provoke enlightenment.
One of his most famous koans is the sound of one hand clapping. It asks, "What is the sound of one hand?" This question is designed to break the disciple's dependence on ordinary logic and to propel them into a state of satori, or sudden enlightenment. It is said that understanding this koan, let alone being able to answer it, can take a student up to three years, reflecting the deep contemplation and internal transformation required in Zen practice.
The intention of a koan is not to be solved like a puzzle but to exhaust the intellectual mind and to open the way for intuitive insight. They are central to Zen Buddhist teaching, and the one Hakuin crafted about the sound of one hand has challenged and inspired Zen students for centuries.