In the matter of physics, the first lessons should contain nothing but what is experimental and interesting to see. A pretty experiment is in itself often more valuable than twenty formulae extracted from our minds.

Conversations with Einstein by Alexander Moszkowski (1971), p. 69. This is just Moszkowski's English translation of a statement he attributed to Einstein in his 1922 book Einstein, Einblicke in seine Gedankenwelt, p. 77: "Was die Physik betrifft, fuhr Einstein fort, so darf für den ersten Unterricht gar nichts in Frage kommen, als das Experimentelle, anschaulich-Interessante. Ein hübsches Experiment ist schon an sich oft wertvoller, als zwanzig in der Gedankenretorte entwickelte Formeln." As Moszkowski makes clear in the original German text, this "quotation" is a paraphrasing of his conversation with Einstein.