I cannot forbear to mention among these precepts a new device for
study which, although it may seem but trivial and almost ludicrous,
is nevertheless extremely useful in arousing the mind to various
inventions. And this is, when you look at a wall spotted with
stains, or with a mixture of stones, if you have to devise some
scene, you may discover a resemblance to various landscapes,
beautified with mountains, rivers, rocks, trees, plains, wide
valleys and hills in varied arrangement; or again you may see
battles and figures in action; or strange faces and costumes, and an
endless variety of objects, which you could reduce to complete and
well drawn forms. And these appear on such walls confusedly, like
the sound of bells in whose jangle you may find any name or word you
choose to imagine.