Leonardo da Vinci has long been lauded as one of the world's greatest thinkers. Not only did he create impeccable artwork (one of which includes the Mona Lisa), he also made his mark as a scientist and engineer, having laid the groundwork for scuba gear and the parachute. Many of his most well-known designs were imagined to as machines of war — like a helicopter, crossbow, and triple-barrel cannon — but as a recent book reveals, the guy also dreamed up a wicked brew for fighting the effects of ageing, too.