Physicists use the wave theory on Mondays, Wednesdays and Fridays and the particle theory on Tuesdays, Thursdays and Saturdays

in David Dietz, The Story of Science, 4th ed. (1942) p. 250. Variant, in C. C. Gaither (ed.) Physically Speaking (1997): "On Mondays, Wednesdays and Fridays we teach the wave theory and on Tuesday, Thursdays and Saturdays the corpuscular theory."