"The cure of a romantic first flame is a better surety to subsequent discretion, than all the exhortations of all the fathers, and mothers, and guardians, and maiden aunts in the universe." -- Fanny Burney, Camilla (1796)
"They called me mad, and I called them mad, and damn them, they outvoted me." -- Nathaniel Lee (late 17c), cited in R. Porter, A Social History of Madness (1987)
"Mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true." -- Bertrand Russell, Mysticism and Logic (1918)
"One must divide one's time between politics and equations. But our equations are much more important to me." -- Albert Einstein, cited by C.P. Snow.
"God and I both knew what I meant once; now God alone knows." -- Friedrich Klopstock (late 18c) [also attributed to Robert Browning]