‹‹‹ Vitr. 3.5.12 | Table of Contents | Vitr. 3.5.14 ›››
13All members over the capitals of columns, such as architraves, friezes, coronæ, tympana, crowning members (fastigia), and acroteria, should not be vertical, but inclined forwards, each a twelfth part of its height; and for this reason, that when two lines are produced from the eye, one to the upper part of a member, and the other to its lower part, the upper line or visual ray will be longer than the lower one, and if really vertical, the member will appear to lean backwards; but if the members are set out as above directed, they will have the appearance of being perpendicular.
13All the members which are to be above the capitals of the columns, that is, architraves, friezes, coronae, tympana, gables, and acroteria, should be inclined to the front a twelfth part of their own height, for the reason that when we stand in front of them, if two lines are drawn from the eye, one reaching to the bottom of the building and the other to the top, that which reaches to the top will be the longer. Hence, as the line of sight to the upper part is the longer, it makes that part look as if it were leaning back. But when the members are inclined to the front, as described above, they will seem to the beholder to be plumb and perpendicular.