Plutarch Artaxerxes 16

[1] Afterwards the eunuch told the matter to Parysatis, and she to the king; and the king was incensed, as being openly convicted of falsehood, and likely to forfeit the fairest and most pleasing feature of his victory. For he wished that all Barbarians and all Greeks should be fully persuaded that when he and his brother had charged and grappled with each other, he had given and received a blow, being only wounded himself, but killing his brother. He therefore gave orders that Mithridates should be put to death by the torture of the boats.

[2]
  Now, this torture of the boats is as follows. Two boats are taken, which are so made as to fit over one another closely; in one of these the victim is laid, flat upon his back; then the other is laid over the first and carefully adjusted, so that the victim’s head, hands, and feet are left projecting, while the rest of his body is completely covered up. Then they give him food to eat, and if he refuse it, they force him to take it by pricking his eyes. After he has eaten, they give him a mixture of milk and honey to drink, pouring it into his mouth, and also deluge his face with it.

[3] Then they keep his eyes always turned towards the sun, and a swarm of flies settles down upon his face and hides it completely. And since inside the boats he does what must needs be done when men eat and drink, worms and maggots seethe up from the corruption and rottenness of the excrement, devouring his body, and eating their way into his vitals.

[4] For when at last the man is clearly dead and the upper boat has been removed, his flesh is seen to have been consumed away, while about his entrails swarms of such animals as I have mentioned are clinging fast and eating. In this way Mithridates was slowly consumed for seventeen days, and at last died.