to plumb the meaning of the kung-an, the student  has
　　   to  abandon  knowledge,   experience,  and  reasoning,
　　   since the answer is not suspectible to these methods.
　　   He must find the answer  by ts'an kung-an   参公案, by
　　   "investigating the king-an. " This
　　  
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　　   requires his sweeping from his consciousness
　　   everything but the kung-an.  When there is nothing in
　　   his mind  but the kung-an, there  is a chance  for an
　　   experience of Ch'an, an awakening.
　　　　  Closely related, but not identical to the  kung-
　　   an, is the hua-t'ou 话头. A hua-t'ou, literally "
　　   head of a thought", is a question   that the meditator
　　   inwardly asks himself. For example, "What is wu?", or
　　   "Who  am I?".  As in the   kung-an, the answer  is not
　　   resolvable  through reasoning, but requires ts'an
　　   hua-t'ou  参话头, "investigating   the hua-t'ou."  The
　　   meditator  devotes his full attention   to repeatedly,
　　   incessantly, asking himself the hua-t'ou. His ou, but
　　   by then Chan-chou had already left, saying nothing.
　　  
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　　　　  Another way kung-an and hua-t'ou are closely
　　   related  is  that  a hua-t'ou   can  give  rise  to  a
　　   king-an, and vice  versa.  For example, the  question
　　   "The 10, 000 dharmas return to One;   to what does the
　　   One return?" was originally a dimple hua-t'ou. Once a
　　   student asked Chao-chou  this same question, to which
　　   the  master  answered,   "The  fabric  I  bought  from
　　   Ch'ing-chou  青州 weighs  seven   chin 斤." A hua-t'ou
　　   became a kung-an because of the interaction   with the
　　   master, and the answer he gave to it.
　　　　  The central or key phrase in a kung-an frequently
　　   serves  as the source for a hua-t'ou.   The often-used
　　   hua-t'ou  "What is wu?", is derived  from Chao-chou's
　　   "Does a dog have Buddha-nature?" kung-an.
　　　　  P'ang Yun 庞蕴 (?-811) a lay disciple of  Ma-tsu
　　   马祖, resolved to follow the Path, threw his   wealth
　　   into the river, and became a  basket   weaver.  While
　　   plying his trade one day, he met a monk begging   for
　　   alms. Giving the  monk  some   money,   Layman  P'ang
　　   asked him, "what is the meaning of   giving  alms? "
　　   The monk said, "I don't know. What is the meaning of
　　   giving alms?" And Layman P'ang   replied,  "Very  few
　　   people have heard about it." The monk   answered,  "I
　　   don't understand." And Layman P'ang asked,   "who  is
　　   it that doesn't understand?" This incident became  a