This book is amazing see site for many more - 1895 - Cusack's freehand ornament. A text book with chapters on elements, principles, and methods of freehand drawing, for the general use of teachers and students . by Armstrong, Charles
Geometry - From Manwithaspade -- This has the look of a drawing exercise on shading but I certainly admire the effort that went into it. I want to color every opening but still have the simplicity of the geometry -- cake and eat it, too.