This study is believed to be a preparatory sketch for a presentation drawing – a new type of drawing that had no preparatory function, but which was considered a work of art in its own right, described by Giorgio Vasari in his biography of Leonardo (1550 and 1568 editions):

“For Segni, his dear friend, he made a drawing of Neptune executed with such draftsmanship and diligence that it seemed absolutely alive. It showed the turbulent sea and Neptune’s chariot drawn by sea horses, with fantastic creatures, sea monsters, and figures of the winds, and some most beautiful heads of marine gods.”

The function of this drawing seems to have been to explore the main figures of the composition, which is one of Leonardo’s most ambitious recreations of classical subject matter. It appears to have been based on the central portion of a Roman sarcophagus from the early third century AD, now in the Vatican, Rome. Leonardo captured the sea god Neptune in a dramatic pose, struggling to control his quadriga of horses.

The sheet contains the artist’s working note to himself along the upper border towards the left, where he writes “abassa i chavalli” (bring down the horses).