A study of the nostrils of a horse, turned three quarters to the right; the upper part of the near hind-leg of a horse and part of the hind-quarter; a hind-leg in profile to the left; a study of the hind-quarters and part of the body of a horse in profile to the left. Melzi's number 47.

During the 1480s Ludovico Sforza, ruler of Milan, commissioned Leonardo to execute a bronze equestrian monument, well over life size, to his father Francesco (1401–66). Ludovico’s first choice for the commission seems to have been the Florentine Antonio del Pollaiuolo. Two drawings by Pollaiuolo for the project date no later than 1484, when Pollaiuolo began work on the tomb of Pope Sixtus IV in Rome, leaving Ludovico to seek another artist.

In July 1489 the Florentine ambassador in Milan wrote to Lorenzo de’ Medici that Ludovico requested the names of other artists who might be more suited to execute the ‘great bronze horse’, as he was not confident of Leonardo’s abilities. Lorenzo replied that there was no-one in Florence suitable, and in time Leonardo overcame Ludovico’s doubts, for in April 1490 he recorded, ‘I recommenced the horse’. An important step in reassuring Ludovico may have been the switch from a rearing horse, unprecedented in a large-scale bronze, to a more conventional walking horse, with left foreleg raised and right hind leg advanced. This new pose is seen in a tiny sketch at lower right of RCIN 912317, inspired by the Roman equestrian monument known as the Regisole (since destroyed) in Pavia, south of Milan.

Leonardo now started to study the form of the horse intensively: drawings from the life in casual poses (RCIN 912310, 912317), details of legs in the intended pose of the monument, and surveys of the horse in orthogonal views (RCIN 912290, 912321). The proportions of the horse evolve from a delicate, skittish type to a heavier build with a more classical head. Leonardo measured individual horses minutely, using as his unit the horse’s head divided into sixteenths. The Sicilian, an admired cavalry horse, appears in several of Leonardo’s measured studies and was probably the breed intended for the monument.

Text adapted from Leonardo da Vinci: A life in drawing, London, 2018