Einstein visited Neils Bohr at home to discuss the fundamentals of quantum mechanics where he noticed a horseshoe above the door.
Einstein asked "What's with the horseshoe?"
Bohr explained that according to folklore it keeps out evil and brings good luck.
Einstein was dismayed: "But you're a man of science! How can you believe in such primitive superstitions?"
Bohr explains, "Of course I know the truth about physics and don't believe this magical horseshoe nonsense. I put the horseshoe up there because I was told it works even if you don't believe in it.