«Optices non ignarus, instructus arithmetica» (Vitr. 1, 1, 3). Una noterella vitruviana: Fra Giocondo, la traduzione di Fabio Calvo per Raffaello e il testo «secondo la volontà dell'autore»

The essay submits to the interest of scholars the problematic nature of the critical editions of Vitruvius’ De architectura, executed in the best of cases (editions of the CUF) on the basis of a stemma codicum of sixteen or twenty codices (out of a total of over 100 mss.). Attention is focused on a short passage from the first book, present as a text in the 1511 edition of Fra Giocondo and, according to ed. CUF, reported by only two codices (of the six main ones). In reality, that marginal addition was not only incredibly misread, but it is also found in quite a few other manuscripts.