 It appears as the Ouroboros, the tail-eater, in the Codex Marcianus, which dates from the tenth or eleventh century, together with the legend 'the One, the All'.Time and again the alchemists reiterate that the "opus" proceeds from the one and leads back to the one, that it is a sort of circle like a dragon biting its own tail.For this reason the "opus" was often called "circulare" (circular) or else "rota" (the wheel).