Euclid

A quantity is said to be a part of a quantity, the less of the greater, when it measures the greater.

And the greater is a multiple of the less when it is measured by the less.

The only purpose of the 'Elements' is to demonstrate mathematically certain fundamental propositions.

For the things of the world cannot be made manifest without the knowledge of mathematics.

Proof by contradiction is a powerful tool.

The prime numbers are more than any assigned multitude of prime numbers.

If a straight line be cut in extreme and mean ratio, the greater segment is also cut in extreme and mean ratio by the lesser segment.

The square on the side subtending the right angle in right-angled triangles is equal to the squares on the sides containing the right angle.

No trace of Euclid's personality has survived.

And the whole is greater than the part.