Abstract
The traditionally represented lambda shape of the two geometrical progressions : 1, 2, 4, 8 and 1, 3, 9, 27 in Plato's Timaeus, the principal source for all irrational proportions used in the Occidental architecuture, reinterpreted as 1, √<2>, 2, 2√<2> and 1, 2/√<3>, 4/3, 8/3√<3>, has been proved the mathematical ground for the Roriczer's method of square and for the Roriczerian method of equilateral triangle formulated and named by the author. The two methods, the two irrational proportions had been the rules for the Geometrical schemes employed mainly in French High Gothic architecture. The rest one irrational proportion genealogized to the Plato's geometrical figures, the golden proportion, is, as well known, the method of Le Corbusier, le Modulor.
