A quotation by Hermann Minkowski

From henceforth, space by itself, and time by itself, have vanished into the merest shadows and only a kind of blend of the two exists in its own right.
Quoted in J R Newman, The World of Mathematics (New York 1956).

The mathematical education of the young physicist [Albert Einstein] was not very solid, which I am in a good position to evaluate since he obtained it from me in Zurich some time ago.

And Einstein? He was always cutting my lectures -- I would never have believed him capable of this.
On the publication of On the Electrodynamics of Moving Bodies.