This is an entertaining exchange about this riddle:
There is a bull charging into an abyss. The horns go in; the head goes in; the
front legs go in; the torso and hind legs go in. But, that tail, it just won't
go in. Why?

I found it at Google Answers

-----Original Message-----
From: Eugene Kelly [mailto:EUGENEKELLY@peoplepc.com]
Sent: Thursday, August 19, 2004 12:50 AM
To: Tolman Brett-ABT033
Subject: Re: bull/tail/abyss

Hello Brett,

I'm sorry about your head. The source of the "bull story" is the Wu-men-kuan (Jap. Mumonkan), lit. "the Gateless Gate"; one of the two most important koan collections of Ch'an (Zen) literature. It was compiled by the Chinese Ch'an (Zen) master Wu-men Hui-k'ai (Jap. Mumon Ekai). Koans (Jap., lit. "public notice") in Chinese Kung-an are paradoxical "riddles" given to students of Ch'an (Zen) meditation by a master for the purpose of aiding the student's progress toward enlightenment. While they are often humorous and interesting, their purpose is considered sacred by Zen Buddhists. By searching for an answer to the Koan it is hoped that the student is propelled beyond the conceptual/logical mind into the "original mind" or "Buddha-nature". There are many koans and, generally, a student's progress is helped by gaining skill at opening the mind into increasing clarity through "solving" koans of greater and greater difficulty.

There are many helpful books on the subject of koans. Your local bookstore probably has several. Or, Amazon.com is another good source.

Best,
Gene Kelly

P.S. I thought you may be one of my new students for the fall semester. That's the reason for the "Prof." earlier. Sorry.
----- Original Message -----
From: Tolman Brett-ABT033
To: 'Eugene Kelly'
Sent: Wednesday, August 18, 2004 8:48 PM
Subject: RE: bull/tail/abyss

Prof. Kelly-
My answer to you should tell you who I am.

Only the stick can tell us what it is.

I went to Caltech from '95 to '99 and this convoluted thinking makes my head hurt.

What's the source of the bull/tail/abyss story?

Please!!!

-Brett

-----Original Message-----
From: Eugene Kelly [mailto:EUGENEKELLY@peoplepc.com]
Sent: Wednesday, August 18, 2004 11:46 PM
To: Tolman Brett-ABT033
Subject: Re: bull/tail/abyss

Well, now that you know "who" I am, who are you? If you can answer that question, you will understand the answer to the riddle.

A teacher holds up a stick and says to his disciples: "Quick, tell me what this is. If you tell me it is a stick, you deny its nature. If you tell me it's not a stick you deny the fact."

Feel free to write back Brett,

Prof. Kelly
----- Original Message -----
From: Tolman Brett-ABT033
To: 'ekelly@roanoke.edu'
Sent: Wednesday, August 18, 2004 5:09 PM
Subject: bull/tail/abyss

Just out of curiosity, from where did you get the 'bull charging' riddle?
I found it in a random Google Answers search a while back, and I figured out who you were.
Thanks for your time,
-Brett
ps. I ask because I feel unsatisfied with the answer.