1961-10-18 NY's Museum of Modern Art displays Henri Matisse's picture "Le Bateau" upside down, takes 47 days and 116,000 people before someone notices
1961-12-04 NY's Museum of Modern Art hangs Henri Matisse's picture "Le Bateau" the right side up, after stock-broker Genevieve Habert notices it is displayed upside down, the first of 116,000 people in 47 days to notice