Albert Einstein’s theory of happiness: He had no cash for a tip, so he gave a note instead which sold for $1.56 million

Albert Einstein, lacking cash for a hotel bellboy in 1922 Tokyo, penned a note on happiness: "A calm and modest life brings more happiness than the pursuit of success combined with constant restlessness." This simple message, intended as a tip, later sold for $1.56 million at auction, proving his playful prediction correct.