5309394 Woodblock engraving depicting a gunner firing a cannon whose elevation had been calculated using a chequered ruler fitted with two plumb-bobs; (add.info.: Woodblock engraving depicting a gunner firing a cannon whose elevation had been calculated using a chequered ruler fitted with two plumb-bobs. The path of a projectile is shown according to Aristotelian physics. Since he believed that no body could undertake more than one motion at a time, the path had to consist of two separate motions in a straight line. Dated 16th century); Universal History Archive/UIG.