Lead is the metal of the underside of the ancient world. It is soft, heavy, cheap and workable at low heat, which made it the material for water pipes, coffin linings, sling bullets, weights and seals, and it turns up in Roman archaeology in quantities no other metal matches. The Latin plumbum survives in the word plumbing and in the chemical symbol Pb.
Its most concentrated ritual use is the curse tablet, the defixio. Several thousand survive from the Greek and Roman world: thin lead sheets inscribed with a binding formula, rolled or folded, often pierced with a nail, and deposited in a grave, a well or a spring. Lead was chosen because it was cheap, because it took a stylus without firing, and, as some of the texts say outright, because it is cold, heavy and useless, qualities the writer wished onto the person named. That is a Saturnine logic stated by the practitioners themselves rather than imposed by later commentators.
Lead was also poison, and was known to be. Vitruvius warns against lead pipes and prefers earthenware. White lead, the carbonate, was nonetheless the standard white pigment and the standard cosmetic base in Europe for two thousand years, and lead acetate, sugar of lead, was used to sweeten wine.
In alchemy lead is where the work begins. It is the base metal, the starting condition many recipes call the prima materia, black and heavy and low, which the sequence exists to lift. The nigredo, the blackening, is Saturn's stage of the work.
Sources Curse Tablets and Binding Spells from the Ancient WorldJohn G. Gager (editor) with The Secrets of AlchemyLawrence M. Principe