Euclid quotes:

The laws of nature are but the mathematical thoughts of God.

That, if a straight line falling on two straight lines makes the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, meet on that side on which the angles are less than two right angles.

There is no royal road to geometry.

Sire, there is no royal road to geometry.

A prime number is one (which is) measured by a unit alone.

QED - Quod erat demonstrandum.

And the whole is greater than the part.

Things which are equal to the same thing are also equal to one another.

A line is length without breadth.

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

Give him threepence, since he must make a gain out of what he learns.

Better balance, less pain and less restless leg syndrome.