“Van de Graaf canon in book design” by jossi – Popularized by Jan Tschichold in his book The Form of the Book in 1975.. Licensed under Public Domain via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Van_de_Graaf_canon_in_book_design.svg#/media/File:Van_de_Graaf_canon_in_book_design.svg