His musings on happiness may not be as famous as his theory of relativity, but still shed light on one of the great modern minds. (Photo: Pixabay)

While Albert Einstein's theory of happiness may be relative, it fetched $1.3 million at a Jerusalem auction.

The Nobel-winning scientist's musings, on a handwritten note, may not be as famous as his groundbreaking theory of relativity, but they still shed light on one of the great modern minds.

The Winner's auction house said Einstein scribbled the note in German to a bellboy while travelling in Japan in 1922 after he did not have the cash to give him a tip.

It says: "A calm and modest life brings more happiness than the pursuit of success combined with constant restlessness."

Today's bidding began at $2,000 and quickly escalated.

Winner's would not disclose the buyer or seller.

Einstein won a Nobel Prize in physics for his theory of relativity. He died in 1955.