A man tries to lift a large heavy rock blocking a road and can't. He waits around for hours and when finally some travellers arrive he declares that none of the

A man tries to lift a large heavy rock blocking a road and can't. He waits around for hours and when finally some travellers arrive he declares that none of them will be able to lift it, it's an impossibly heavy rock. One of the travellers lifts the rock and everyone is pleased they can move on, but not before the original man shouts: "I'd have done it myself if only I tried hard enough."