It is easier to square the circle than to get round a mathematician.
Quoted in H Eves In Mathematical Circles (Boston 1969).
I don't quite hear what you say, but I beg to differ entirely with you.
Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.
A Budget of Paradoxes.
Imagine a person with a gift of ridicule [He might say] First that a negative quantity has no logarithm; secondly that a negative quantity has no square root; thirdly that the first non-existent is to the second as the circumference of a circle is to the diameter.
The moving power of mathematical invention is not reasoning but imagination.