Similes of Attainment Though to the extent of my admittedly scarce knowledge, decapitation as a simile for some level of attainment is not to be found in the Pali Canon, but I bet the Zen tradition offers countless koans and stories wherein, figuratively, the incumbent experiencer of realization is beheaded, very much to his surprise I would say.

If you happen to know a few of these stories, your kind attention in helping me digging out these similes is greatly appreciated.

My gratitude for having taken the time to read this.
There are two that come to mind from the Shoyoroku.  The first is Case 98 and it's entitled Tonzan's Heed.  In that instance, it more refers to reticence on the part of the teacher in not wanting to lead the student into intellectualism.  I'm not sure if that is the image you were after. The second is at Case 41:


  When he was about to die, Rakuho addressed his assembly and said, “I
  have one matter to ask you about. If you say ‘yes’ to this, you are
  putting another head on your own. If you say ‘no,’ you are looking for
  life by cutting off your head.”


I don't think this is what you are looking for exactly, either.  

I can't think of a single koan in the Mumonkan or Hekiganroku that has an image like that, however.  But kicked into mud?  Cat cut in two?  Finger cut off?  Nose pinched?  Now that's a different story!  

(Note: the Shaseki-shu has something about heads being cut off.  Unfortunately, that collection does not contain any actual koans.  Those are parables.)