Lithium carries no alchemical inheritance: it was unknown as an element until the nineteenth century, long after the planetary-metal scheme had closed, so no ancient symbolism attaches to it. Its cultural resonance is entirely modern and twofold. In cosmology, lithium is one of only a handful of elements forged in the first minutes after the Big Bang, alongside hydrogen and helium, which gives it a quiet place in accounts of the universe's origin.
In medicine, lithium salts became, after John Cade's work in 1949, the archetypal mood stabiliser, so that the element's name entered ordinary speech as a byword for psychiatric steadiness. A parallel thread runs through the patent-medicine era: from the 1880s American spa towns such as Lithia Springs, Georgia marketed naturally occurring lithium-bearing water as a cure-all, and in 1929 the soft drink that became 7 Up launched under the name Bib-Label Lithiated Lemon-Soda, containing lithium citrate and advertised as a mood-lifting tonic; the ingredient was quietly removed only in 1950, decades before Cade's clinical work put lithium's psychiatric effect on a scientific footing. The element also has a harder modern use: lithium-6 deuteride is the fusion fuel of thermonuclear weapons, so the lightest of metals sits at both extremes of human use, tonic water and doomsday device.