Perspective is a most subtle discovery in mathematical studies, for by means of lines it causes to appear distant that which is near, and large that which is small.

Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer.

The earth is moved from its position by the weight of a tiny bird resting upon it.

Being engulfed in practice without delicate knowledge related to it, is in many ways like entering a ship without knowing where it is headed.

Weight is caused by one element being situated in another; and it moves by the shortest line towards its centre, not by its own choice, not because the centre draws it to itself, but because the other intervening element cannot withstand it.

Threats alone, are the weapons of the threatened man.

Nature is constrained by the cause of her laws which dwell inborn in her. Variant: Nature is constrained by the order of her own law which lives and works within her.