One of the most straightforward routes to eternal life involves locating the mythical Fountain of Youth, a spring that allegedly has the power to restore the elderly to adolescence. The font has piqued the interest of European explorers since at least the classical period in antiquity, with especially concerted efforts to find it (supposedly) made by the Spanish conquistadores of the 16th century. Instead they found Florida, which is today home to one of the largest populations of elderly people in the United States.

From the Qin through the Ming dynasty, countless Chinese nobles and other elites — including at least six Tang dynasty emperors — died from consumption of elixirs of eternal life that contained substances like mercury, lead, gold, silver, cinnabar, copper carbonate, vitriol, sulfur, sulfuric acid, arsenic, arsenic sulfide, and more. Contemporaneous texts describe some of the key symptoms of metallic poisoning (like the sensation of insects crawling over the body) as firm proof that the elixirs were working.

The medieval Italian humanist Marsilio Ficino advised consuming the blood of a willing juvenile in order to turn back the biological clock. “Why shouldn’t our old people, namely those who have no recourse . . . suck the blood of a youth?” he asks, presumably rhetorically, in his 1489 text De Vita. For taste, he recommends boiling the concoction to cut the bitterness and then mixing the blood with sugar and water. According to legend, a dying Pope Innocent VIII took it one step further in 1492 and injected fresh young blood directly into his veins; he died regardless.