the sacred cista, its lid half-opened, a snake emerging… The cista of the coin and the cista of Erichthonios are one and the same; the myth arose from a rite.
Harrison argues that the cistophoric coins of Ephesus prove that the Dionysiac cista with its emerging snake is structurally identical to the Erichthonios myth, establishing the principle that myth derives from ritual practice.
, Themis: A Study of the Social Origins of Greek Religion, 1912thesis