A classic representation of Charon's obol, a coin that paid for the ferry across the Acheron--the river dividing the living and the dead. Characteristics: it is a single, low-denomination coin; it is placed in the mouth; the placement occurs at the time of death; it represents a boat fare. This is almost certainly why Greg and Wirt needed two pennies to ride the ferry to Adelaide's. Charon and Psyche - 1883, Stanhope