Codex Forster III, c. 1490-1493. "Codex Forster III was compiled between about 1490 and 1493, when Leonardo was in the service of Ludovico Sforza, Duke of Milan. It is the most miscellaneous of all the Leonardo notebooks held by the V&A. Notes and diagrams on geometry, weights and hydraulics are interspersed with jottings and sketches on diverse subjects such as locking devices (folios 42 recto, 54 verso, or 75 recto), architecture (see folio 55 verso), costumes and hats (folios 8 verso – 10 recto), and human and animal anatomy. On folio 28 recto, for example, a drawing shows the hair and layers of skin on a human head.
It also includes recipes for artistic practice, explaining for instance how to prepare linseed oil with mustard seed (folio 10 verso), and mentions books of interest owned by other people, as in the case of a 'fine herbal' belonging to a certain Giuliano da Marliano (folio 37 verso).
As Leonardo wrote in mirror writing (in reverse and from right to left), he usually started with what we would consider the last page. He also occasionally used his notebook upside down, as for instance towards the end of the volume (see folios 72 verso – 88 verso).