**2. Materials and Methods**

## *2.1. Drawing 8P*

*Drawing 8P* (Uffizi Gallery), named after its inventory number, is considered by many to be the first known drawing by the great Tuscan artist and scientist Leonardo da Vinci. He is believed to have depicted the landscape on the front side or recto of the sheet (Figure 1a) when he was twenty-one-years-old and still an apprentice at the prestigious Florentine workshop of Verrocchio. The autograph heading on the top-left margin (Figure 1a, region *i*), "*Dì di s[an]ta Maria della neve/addj 5 dhaghossto1473*", written in Leonardo's typical right-toleft handwriting, indicates the date and the feast associated with the creation of the drawing (5 August 1473, Day of Our Lady of the Snow) [28]. This inscription makes *Drawing 8P* the only known landscape by Leonardo with an autograph date. There is a signature in the lower right corner of the sheet, which is considered apocryphal, possibly added at the end of the 16th century, and related to the collecting history of the drawing. There is no visible sign of watermarks on the paper, thus making it impossible to determine the area of its provenance. Little is known about the drawing's conservation history, due to the absence of attested documentation, such as technical and restoration reports. The circular stamp of the Uffizi collection is still visible in the bottom-left corner of the recto, dating to an old mounting of the drawing on a dark card, which is now missing. The small size of the sheet (around 19 × 28 cm), as well as the complexity of the composition, namely a view from above, suggest that the landscape was made in a workshop rather than outdoors. The scene is constructed through the sum of several elements, starting from the arid terrain with a few isolated trees in the foreground that opens the perspective on a rocky wall with a waterfall (on the right) and a promontory topped by a fortified citadel (on the left). A marshy area with grazing animals on the mainland is represented in the background, with outlines of hills and turreted villages fading into the distance. Leonardo's exceptional drawing skills and speed of execution are made evident by the clear strokes synthesizing each detail, with the sfumato technique, invented by the artist himself, giving the whole scene a sense of vibrant suspension. The back of the sheet or verso (Figure 1b), on the other hand, shows a series of undefined figures and shapes, which have been mostly ignored by scholars in favor of the more evocative landscape on the recto. However, the group of hills with a river and a bridge sketched in the middle of the sheet is considered the initial idea of the landscape later developed on the front [28]. Faded sketches of a female bust and a man's head are also outlined with red chalk on the up-right margin of the folio. Among the traces of geometric figures depicted on the left, one was identified as an early study of Leonardo's famous knots. The left-to-right written inscription on the top margin (Figure 1b, region *ii*) was attributed to Leonardo and thus considered proof of his ability to write with both hands [28].
