Sir Isaac Newton.

1025. Newton could not admit that there was any difference
between him and other men, except in the possession of such
habits as ... perseverance and vigilance. When he was
asked how he made his discoveries, he answered, "by always
thinking about them;" and at another time he declared that
if he had done anything, it was due to nothing but industry and
patient thought: "I keep the subject of my inquiry constantly
before me, and wait till the first dawning opens gradually, by little and little, into a full and clear light." WHEWELL, W.

History of the Inductive Sciences, Bk. 7, chap. 2,
sect. 5.

1026. Newton took no exercise, indulged hi no amusements,
and worked incessantly, often spending eighteen or nineteen
hours out of the twenty-four in writing. BALL, W. W. R.

History of Mathematics (London, 1901), p. 858.

source: Memorabilia mathematica; or, The philomath's quotation-book - Moritz, Robert Édouard, 1868-1940