[255] Mercurius was first understood pretty well everywhere as hydrargyrum1 (Hg), quicksilver or argentum vivum (Fr. vifargent or argent vive). As such, it was called vulgaris (common) and crudus. As a rule, mercurius philosophicus was specifically distinguished from this, as an avowedly arcane substance that was sometimes conceived to be present in mercurius crudus, and then, again, to differ from it completely. It was the true object of the alchemical procedure. Quicksilver, because of its fluidity and volatility, was also defined as water. A popular saying is: “Aqua manus non madefaciens” (the water that does not make the hands wet).2 Other designations are aqua vitae,3 aqua alba,4 aqua sicca.5 The last designation, dry water, is paradoxical, for which reason I should like to call special attention to it as characterizing the nature of the object described. Aqua septies distillata (seven times distilled water) and aqueum subtile6 point to the sublimated (“spiritual”) nature of the philosophic Mercurius. Many treatises simply speak of Mercurius as water.7 The doctrine of the humidum radicale (root-moisture or radical moisture) underlies such designations as humidum album,8 humiditas maxime permanens incombustibilis et unctuosa,9 and humiditas radicalis.10 Mercurius is also said to arise from the moisture like a vapour11 (which again points to his spiritual nature), or to rule the water.12 The “divine water” (ὕδωρ ϑεῑον) so often mentioned in the Greek texts is quicksilver.13 Mercurius as the arcane substance and golden tincture is indicated by the designation aqua aurea14 and by the description of the water as Mercurii caduceus.15