The 4th International Laboratory for the History of Science
Art, Science and Techniques of Drafting in the Renaissance

Protocol Wednesday, 30 May 2001
(by Simona Cremante, Fabio Frosini and Giovanni Masucci)

Romano Nanni introduces the session in the Leonardian Library in Vinci .

Carlo Pedretti after the welcome speech praises this library which was founded in the late 1880s. He then discusses the birth of the Leonardian Library thanks to the Uzielli legacy. He stresses that the aim will be to take up new aspects and challenges in Leonardo Studies.
He starts by looking at Codex Atlanticus (formerly 191r-a and r-b). In these sheets there are some interesting sketches that allow us to understand the movement of Leonardo's mind. On a related page, from c. 1490 (formerly 191r-b), we find drawings that recall the mazzocchio in perspective, with anologies with Barbaro (1569) and Sirigatti (1596) for its dynamic construction. Leonardo refers to this three-dimensional object as a body born from perspective without relation to any body but out of simple lines only. In this spiral form he investigates the continuous quality of the line. In the bigger mazzocchio (CA 191 r- a) we see also some little pyramids on the inner face of the mazzocchio.
On the subject of perspective and the knowledge of the artist it is also important to remember the influence of the scholastic tradition and medieval skills about optics, for example Ghiberti, who commented on Alhazen, Bacon, Witelo etc.
These drawings may be usefully compared to other studies by Leonardo, such as the skulls presented like extremely precise solid bodies in the Windsor royal collection.

Antonio Natali - Annunciazione in the Uffizi: Natali proposes to consider the painting as having been conceived for a specific point of view. Instead of the traditional frontal view Leonardo could have considered a sideview from the right, and perhaps slightly from below. In fact, from direct observation the entire composition appears unbalanced and seems to show some distortions e.g. in the right arm of the Virgin and the architecture behind.This hypothesis of a fixed lateral viewpoint could match with the original destination of the panel that still remains unknown.

Rocco Sinisgalli - The second part of the morning was devoted to a discussion about the golden section in the famous drawing of the Vitruvian Man in the Galleria dell'Accademia of Venice. The starting point was that in this drawing, showing the superimposing of the two moments of the Vitruvian demonstration, the center of the square and that of the circle don't coincide. Is this an anomaly or an incoherence? Everything seems to be explained, according to Sinisgalli, through recourse to Ptolemy's De Analemmate. Sinisgalli proceedes with a demonstration of the geometrical construction of the way to determine the circle from the square and vice versa. In this process the golden section rule plays the fundamental role. At the end of the demonstration the centerpoints of square and circle are determined respectively in the pubis and in the navel.

Discussion - According to Hoffmann the concept in the Vitruvian Man recalls some sentences in Plato's Timaeus about proportions (see 31 b -32 a "Quello ch'è nato deve essere corporeo e visibile e tangibile. […] Non è possibile che due cose sole si compongano bene senza una terza: bisogna che in mezzo vi sia un legame che le congiunga entrambe. E il più bello è quello che faccia per quant'è possibile , una cosa sola di sé e delle cose legate: ora la proporzione compie questo in modo bellissimo. Perché quando di tre numeri o masse o potenze quali si vogliano, il medio sta all'ultimo come il primo al medio, e d'altra parte ancora il medio sta al primo , come l'ultimo al medio, allora il medio divenendo primo e ultimo e l'ultimo il primo divenendo a lor volta medi ambedue così di necessità accadrà che tutti siano gli stessi e divenuti gli stessi fra loro, saranno tutti una cosa sola").
In reference to Sinisgalli's hypothesis Galluzzi and Pedretti suggested that the original sheet be consulted to look for the presence of traces left by the point of the compass that might verify the hypothesis.
Woodward refers back to the CA 191 r-b, stressing that it clearly deals with the representation of the terrestrial globe on a flat surface. Carlo Pedretti provides a reading of the text referring to the drawing that involves essentially the principles of cartography according to Ptolemy's second projection.

Pedretti next talks about the experiences of drafting dealing mostly with technology and science in Verrocchio's workshop.The main focus was on the role of the bottega (workshop). He goes on to quote from Libro di Pittura § 47 where Leonardo illustrates the comparison between painting and sculpture (il paragone delle arti), underlining the importance for the artist of acquiring a specific drafting skill before recurring to any instrument like the prospectographer.
Considering the painting of the Annunciazione, it's important to remember that the architect Giambattista Caporali, who probably met Leonardo in Rome between 1513 and 1516, reports Leonardo's words as follows: "and in our time Leonardo Vinci of Florence, with whom we have spoken about perspective, and he affirms that he does it, more than anyone else, with two centers, or, rather, vanishing points".

Paolo Galluzzi makes a general remark about the importance of the center of gravity in Leonardo's way of painting figures, and indicates the particular relationship with the issues of sculpture. The problem of balancing and of weight in the representation of human bodies was surely already experienced by the young Leonardo in Verrocchio's workshop.