Book 4
6.2
2. Further, the jambs themselves should be diminished at the top by one fourteenth of their width. The height of the lintel should be equivalent to the width of the jambs at the top. Its cymatium ought to be one sixth of the jamb, with a projection equivalent to its height. The style of carving of the cymatium with its astragal should be the Lesbian. Above the cymatium of the lintel, place the frieze of the doorway, of the same height as the lintel, and having a Doric cymatium and Lesbian astragal carved upon it. Let the corona and its cymatium at the top of all be carved without ornamentation, and have a projection equal to its height. To the right and left of the lintel, which rests upon the jambs, there are to be projections fashioned like projecting bases and jointed to a nicety with the cymatium itself.
6.3
3. If the doorways are to be of the Ionic style, the height of the aperture should be reached in the same manner as in the Doric. Let its width be determined by dividing the height into two and one half parts and letting one of them form the width at the bottom. The diminutions should be the same as for Doric. The width of the faces of the jambs should be one fourteenth of the height of the aperture, and the cymatium one sixth of the width. Let the rest, excluding the cymatium, be divided into twelve parts. Let three of these compose the first fascia with its astragal, four the second, and five the third, the fasciae with their astragals running side by side all round.
