Gisan Zenkai was a Zen

Zen

Zen is a school of Mahāyāna Buddhism founded by the Buddhist monk Bodhidharma. The word Zen is from the Japanese pronunciation of the Chinese word Chán , which in turn is derived from the Sanskrit word dhyāna, which can be approximately translated as "meditation" or "meditative state."Zen...

 Master in 19th century Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. He taught in Okiyama. The most famous story about him concerns his conversation in 1837 with the disciple cooling his bath: this is given in an abbreviated version in Zen Flesh, Zen Bones, and in more expanded version in other sources (such as this). The Zen Flesh, Zen Bones version is:

"A Zen master name Gisan asked a young student to bring him a pail of water to cool his bath.

"The student brought the water and, after cooling the bath, threw on to the ground the little that was left over.

"'You dunce!' the master scolded him. 'Why didn't you give the rest of the water to the plants? What right have you to waste even a drop of water in this temple?'

The young student attained Zen in that instant. He changed his name to Tekisui Giboku (1822—1899), which means a drop of water."

Gisan was also the teacher of masters Ekkei Shuken, Daisetsu Joen, and Ogino Dokuen.