The Van de Graaf canon is a historical reconstruction of a method that may have been used in book design to divide a page in pleasing proportions. This canon is also known as the “secret canon” used in many medieval manuscripts.
The geometrical solution of the construction of Van de Graaf’s canon, which works for any page width:height ratio, enables the book designer to position the text body in a specific area of the page. Using the canon, the proportions are maintained while creating pleasing and functional margins of size 1/9 and 2/9 of the page size.
The resulting inside margin is one-half of the outside margin, and of proportions 2:3:4:6 (inner:top:outer:bottom) when the page proportion is 2:3 (more generally 1:R:2:2R for page proportion 1:R). This method was discovered by Van de Graaf, and used by Tschichold and other contemporary designers; they speculate that it may be older.