Aurea Sectio (the golden section) or mean ratio of a line segment AB, is that part AX that is the proportional average between the entire segment and the remaining XB part. While the terms extreme and mean ratio are attributed to Euclide, the expression Aurea Sectio is attributed to M.Ohm (1835) and is, in any event, linked to the concept of aesthetic perfection that, during the Renaissance, was attributed to the ratio between a section and its Aurea Sectio. Luca Pacioli called this golden ratio the "divine proportion" (in his Divina Proportione, 1496) and wanted to make it the basis for the aesthetic proportion of a building and, at the same time, the human body. So, in the precepts of Leonardo's and Durer's works, the navel divides the total height according to the Aurea Sectio. For 16th century draughtsmen, the golden ratio is the ratio of perfect proportions, which best relates to the concept of "unity in diversity". Later, less importance was given to this type of mathematical ratio until the advent of contemporary formalism that attempts to define universally valid metric laws. This led to the re-evaluation of the golden ratio by Le Corbusier, in his "modulor" proportion theory and in the modern movement of the so-called "section d'or".