Washington DC Monumental Core Shown to Be
One Fundamental Mystery
The Canon asserts that it is unquestionable that there was a canonical art of building, and that it depended on one fundamental mystery. As direct evidence of the old mystical rule of building, the author presents two illustrations taken from Cesarino's edition of Vitruvius (a first century, Roman architect), published in 1521, which depicts the elevation and floor plan for the Milan Cathedral, claiming that they are "an most important illustration of the principles of architecture of all peoples".
According to the book, the geometric figure forming the plan of the Milan Cathedral is the rhombus, invisibly introduced into the plan as the mystical complement of the cross, emblems of the double soul of the Universe, of the two mysterious factors of existence.
On page 204, the author repeats his claim that "according to the system of Cesario applied to Milan Cathedral the rhombus formed the basis upon which the plan for the church was constructed". Clearly he is speaking of the elevation and not the floor plan, because, as you can see, the floor is a grid of squares. Note that the circle that I have drawn at the center of the crossing of the nave and transcepts contains both a square and an octogon.
[Note also that the diagonals of the double square do not form the same ratio as the vesica. In the double square, the 1: 2 ratio is between the two short sides of the triangle, while the rhombus formed by the vesica has the short side being half the hypotenuse.]
Being a two dimensional figure, the square, the first measureable surface, is appropriate for the floor, while it's cousin the cube is appropriate for 3D space. Note the squares and rectangles in the image below, which mirrors those in the cathedral plan above.