Excerpt: "Leonardo Da Vinci found in drawing the readiest and most stimulating way of self-expression. The use of pen and crayon came to him as naturally as the monologue to an eager and egoistic talker. The outline designs in his " Treatise on Painting" aid and amplify the text with a force that is almost unknown in modern illustrated books. Open the pages at random. Here is a sketch showing " the greatest twist which a man can make in turning to look at himself behind." The accompanying text is hardly needed. The drawing supplies all that Leonardo wished to convey."