You should look at certain ...

You should look at certain walls stained with damp, or at stones of uneven color. If you have to invent some backgrounds you will be able to see in these the likeness of divine landscapes, adorned with mountains, ruins, rocks, woods, great plains, hills and valleys in great variety; and expressions of faces and clothes and an infinity of things which you will be able to reduce to their complete and proper forms. In such walls the same thing happens as in the sound of bells, in whose stroke you may find every named word which you can imagine.
You should look at certain walls stained with damp, or at stones of uneven color. If you have to invent some backgrounds you will be able to see in these the likeness of divine landscapes, adorned with mountains, ruins, rocks, woods, great plains, hills and valleys in great variety; and expressions of faces and clothes and an infinity of things which you will be able to reduce to their complete and proper forms. In such walls the same thing happens as in the sound of bells, in whose stroke you may find every named word which you can imagine.

Quotes from the same author

All our knowledge has its origins in our perceptions.
It had long since come to my attention that people of accomplishment rarely sat back and let things happen to them. They went out and happened to things.
Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.
Nothing strengthens authority so much as silence.
He who is fixed to a star does not change his mind.