Leonardo da Vinci created designs for mortars that improved upon the current military technology.  Cannons of the day shot large, solid spheres. To increase the efficiency of the mortar, da Vinci designed projectiles that contained mini gunpowder shots. The shots were packed into petal-shaped iron pieces that formed a ball. The cannonball was loaded into the mortar and fired. da Vinci designed more effective projectiles including shells that exploded upon impact or scattered projectiles over an area. His drawing shows a front mortar firing bombs that explode on impact into a cloud of metal shrapnel. The back mortar loaded with stones or small-caliber iron balls that are fired at the enemy like grape-shot. One of his earlier designs was a mortar mounted on a boat for naval combat. His designs are thought to be the precursor to machine guns.