I've heard a story, which runs like the following, from a colleague:
Some monk was meditating in a beautifully painted cave. A person came and asked him: "How can you concentrate in such a place?" The monk replied: "Oh, I didn't notice that there are paintings."
This is an interesting story for me, but since that colleague himself heard the story from somebody else, he couldn't tell me the exact source.
If any of you can think of a possible source, I'd very much appreciate the reference. Thank you for any help.