Just as a well-filled day brings blessed sleep, so a well-employed life brings a blessed death - Leonardo da Vinci

As a well-spent day brings happy sleep, so life well used brings happy death.

If you transmit the rays of the sun through a hole in the shape of a star you will see a beautiful effect of perspective in the spot where the sun's rays fall.

Those who are in love with practice without knowledge are like the sailor who gets into a ship without rudder or compass and who never can be certain whether he is going. Practice must always be founded on sound theory, and to this Perspective is the guide and the gateway; and without this nothing can be done well in the matter of drawing.