Art du trait. Considerations on double orthogonal projection in medieval stereotomy

The ancient art of stereotomy lies at the origins of the long process of formalizing the method of double orthogonal projection, which found its conclusion at the end of the nineteenth century with Gaspard Monge (1746-1818). Beginning from some statements contained in the famous Dictionnaire raisonné of Eugène Emmanuel Viollet-le-Duc (1814- 1879), and in particular under the entry ‘Trait (art du)’ the current essay discusses the hypothesis of the use of rigorous projection techniques in the Gothic building site and the ante litteram knowledge of descriptive geometry on the part of medieval artisans. On this theme, the essay offers some considerations regarding the restoration architect’s hypotheses, by considering them in view of more recent studies by Italian and French authors in the field of the history of architectural drawing and the history of the codification of forms of representation.