Greek alchemists used what they called ὕδωρ θεῖον, meaning both "divine water", and "sulphurous water". For Zosimos, the alchemical vessel was imagined as a baptismal font, and the tincturing vapours of mercury and sulphur were likened to the purifying waters of baptism, which perfected and redeemed the Gnostic initiate. Zosimos drew upon the Hermetic image of the "krater" or mixing bowl, a symbol of the divine mind in which the Hermetic initiate was "baptized" and purified in the course of a visionary ascent through the heavens and into the transcendent realms. Similar ideas of a spiritual baptism in the "waters" of the transcendent pleroma are characteristic of the Sethian Gnostic texts unearthed at Nag Hammadi. This image of the alchemical vessel as baptismal font is central to his "Visions", discussed below.