I watched a Netflix special on Hindu yogis recently. There was this one whose practice consisted entirely of holding his arm up permanently. He had literally held his arm up for years, so that it had essentially withered and petrified in that position. I do not believe he could have lowered it anymore even if he wanted to.
I realize that this is only tangential to your post, but the show really got me thinking about the relationship of the body to the path. Some (like ascetics) seem to see the body as an impediment, something to be shunned and even tortured in order to demonstrate lack of attachment to it. Others (like Taoists) strive to perfect the body through practices like qigong in order to make it an ideal vessel for expressing the inner self.
Personally, the latter school of thought makes a lot more sense to me.
RE: Zen koan of the day - Moshi's Hand