The principal study on this sheet depicts, in cutaway, a mechanical boat operated by two men (one obscured by ink dribbled across the sheet). The men seem to be turning a large horizontal wheel, geared to a smaller vertical wheel on a transverse axle, while the man in the stern is leaning against another transverse axle bearing a toothed wheel. A chain running from the middle of the boat to the bow may be some folding mechanism, which would explain the sketch to the right, of a man carrying on his back what seems to be a folded boat. At centre is a figure with a tight-fitting seal around his waist; long faint lines to either side suggest this might be some sort of canoe.

Leonardo’s career coincided with the introduction of gunpowder into European warfare, and his many military drawings of the 1480s (see RCIN 912647, 912649-912653) include designs for both the old type of weapon – lances, chariots, enormous catapults and crossbows – and the new – guns, cannon and mortars. It is unlikely that any of these designs was put into practice, and indeed Leonardo could be dismissive of such inventions, noting that ‘they often do no less damage to one’s friends than to one’s enemies’.

A number of his ideas were derived from woodcuts in a printed edition of Roberto Valturio’s De re militari, a treatise on warfare written around 1450 and published from 1472 onwards, an edition of which was owned by Leonardo. He may have been considering producing a treatise of his own, with designs improving upon those illustrated in Valturio.

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