“When [Born and Heisenberg and the Göttingen theoretical physicists] first discovered matrix mechanics they were having, of course, the same kind of trouble that everybody else had in trying to solve problems and to manipulate and to really do things with matrices. So they had gone to Hilbert for help and Hilbert said the only time he had ever had anything to do with matrices was when they came up as a sort of by-product of the eigenvalues of the boundary-value problem of a differential equation. So if you look for the differential equation which has these matrices you can probably do more with that. They had thought it was a goofy idea and that Hilbert didn’t know what he was talking about. So he was having a lot of fun pointing out to them that they could have discovered Schrödinger’s wave mechanics six month earlier if they had paid a little more attention to him.”

Constance Reid Hilbert (Springer-Verlag, 1996) [ISBN 0-387-94674-8] p. 182. Also quoted in Max Jammer, The Conceptual Development of Quantum Mechanics (McGraw-Hill, 1966) pp. 207-208. Jammer cites the original reference: Edward U. Condon 60 Years of Quantum Physics, Physics Today 15 37-49 (1962)