Leonardo da Vinci

Thou, O God, dost sell us all good things at the price of labor.

Let proportion be found not only in numbers and measures, but also in sounds, weights, times, and positions, and what ever force there is.

It is easier to resist at the beginning than at the end.

You will never have a greater or lesser dominion than that over yourself. . . . the height of a man's success is gauged by his self-mastery; the depth of his failure by his self-abandonment. . . . And this law is the expression of eternal justice. He who cannot establish dominion over himself will have no dominion over others.

Where the spirit does not work with the hand, there is no art.

Shun those studies in which the work that results dies with the worker.

Whoever despises the high wisdom of mathematics nourishes himself on delusion and will never still the sophistic sciences whose only product is an eternal uproar.

Inequality is the cause of all local movements.

Mechanics is the paradise of the mathematical sciences, because by means of it one comes to the fruits of mathematics.

No human investigation can be called real science if it cannot be demonstrated mathematically.