http://retinart.net/graphic-design/secret-law-of-page-harmony/

“The easiest to draw and possibly the first to be explicitly used for the book, the Van de Graaf canon is the one most often seen when page canons are discussed”…
“What Van de Graaf discovered was that no matter the size of the page, or the ratio it took, his canon will always result in the top left corner of the textblock being 1/9th form the top and 1/9th from the inside margin, ensuring that the textblock will be positioned consistency and with balance and harmony.”..