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

Mathematics reveals its secrets only to those who approach it with pure love, for its own beauty.

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

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.

How many theorems in geometry which have seemed at first impracticable are in time successfully worked out!

Eureka! (I have found it!).

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