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

All our knowledge has its origin in our perceptions

Having wandered some distance among gloomy rocks, I came to the entrance of a great cavern ... Two contrary emotions arose in me: fear and desire — fear of the threatening dark cavern, desire to see whether there were any marvelous things in it.

If you wish to make a figure in marble, first make one of clay, and when you have finished it, let it dry and place it in a case which should be large enough, after the figure is taken out of it, to receive also the marble, from which you intend to reveal the figure in imitation of the one in clay.