"The Burial Customs of the Ancient Greeks"
As soon as death had laid hands upon the victim, the relatives or friends, after gently closing the eyes of their loved one, inserted, in the dead man’s mouth, the obol, a coin valued at about three half pence, or about three cents of our money, which was to serve as passage money over the Styx. They were very careful not to overlook this duty, since it was believed that, if old Charon could not collect his ferriage, the unlucky shade would be sent back to life.
They also examined the coin closely, to see whether it would pass current among the inhabitants of the lower world.
An admirable verification of this custom was, in this century, excavated in the town of Samos in Cephallenia. A tile coffin dug up at that place was found to contain the bones of an initiate of the Bacchic mysteries and between the back teeth of the skull, thedanake, a coin, somewhat more in value than an obol, was still firmly lodged. The late excavations in Italy, Greece and Asia have revealed numerous coins in the tombs. The painting on a vase, which is described by Pottier, shows a small coin held between the thumb and fore finger of the figure which represents the deceased. In the “Frogs” of Aristophanes, Dionysus is told by Heracles, who has returned from the lower regions, that he will be obliged to pay two obols as ferriage, since his servant, Xanthias, is with him.