The centre of gravity of any parallelogram lies on the straight line joining the middle points of opposite sides.

The diameter of the earth is greater than the diameter of the moon and the diameter of the sun is greater than the diameter of the earth.

Rise above oneself and grasp the world.

Two magnitudes whether commensurable or incommensurable, balance at distances reciprocally proportional to the magnitudes.

Give me but a firm spot on which to stand, and I shall move the earth.

Those who claim to discover everything but produce no proofs of the same may be confuted as having actually pretended to discover the impossible.

I am persuaded that this method [for calculating the volume of a sphere] will be of no little service to mathematics. For I foresee that once it is understood and established, it will be used to discover other theorems which have not yet occurred to me, by other mathematicians, now living or yet unborn.