I still think of this one whenever some lab apparatus starts working after an expert walks in and fiddles with some wires or power-cycles it --
A novice was trying to fix a broken lisp machine by turning the power off and on.
Knight, seeing what the student was doing, spoke sternly -
"You can not fix a machine by just power-cycling it with no understanding
of what is going wrong."
Knight turned the machine off and on.
The machine worked.Funnily, esr also maintains/mirrors those koans as part of the Jargon Files. http://www.catb.org/jargon/html/koans.html
After Zen master Yuanwu's Blue Cliff Records - collection of 100 classical koans with his commentary verses - started to spread around, his successor Dahui noticed how monks and laypeople treated the collection as intellectual and artistic work (Yuanwu Keqin wrote and spoke very beautifully, so they do have artistic value) and burned all copies he could find.
The original use of koan is to be meditation aid (huatou-method, koan practice) not subject of philosophical inquiry.
ps. The original MIT AI lab koans are more clever than these ESR ones. http://groups.csail.mit.edu/mac/users/dae/notes/ai-koans