A Koan is a story or question
used to free the mind of logical perception; koans are neither obscure
nor enigmatic. They are often used by teachers as a tool
to let their students experience true insight.
koan cannot be understood by logic; it cannot be transmitted in words;
it cannot be explained in writing; it cannot be measured by reason. It
is like a great fire that consumes all who come near it."
(Chung-feng Ming-pen [1263-1323] quoted in Miura and Sasaki 1966:5)
A Collection of Koans: