A man noticed Nasrudin digging a hole, and asked him about it.
The reply was, “I buried something in this field last month, and I’ve been trying to find it all morning.”
“Well,” said the other, “did you have some kind of marking system for it.”
Nasrudin said, “Of course I did! When I was burying it, there was a cloud directly over it that cast a shadow—but now I can’t find that cloud, either!“