Pauli thought Heisenberg’s ‘World Formula’ needed a lot more work, and he made his point graphically. He sent this drawing of an empty picture frame to George Gamow on 1 March 1958 with the caption, ‘This is to show the world that I can paint like Titian … Only technical details are missing.’
Pauli and Heisenberg had collaborated for many years, but Pauli was unconvinced by the results of their search for a unified theory of elementary particles, and felt the publicity about it was premature. He died in December of the same year. The letter is online here.