The Deipnosophists (2.6)

But Philochorus says that men who drink hard do not only show what sort of disposition they themselves are of, but

do also reveal in their chattering the characters of every one else whom they know. Whence comes the proverb,

Wine and truth;[*]

and the sentence,

Wine lays bare the heart of man.

And so in the contests of Bacchus the prize of victory is a tripod: and we have a proverb of those who speak truth, that

they are speaking from the tripod;

in which the tripod meant is the cup of Bacchus. For there were among the ancients two kinds of tripods, each of which, as it happened, bore the name of λέβης, or bowl; one, which was used to be put on the fire, being a sort of kettle for bathing, as Aeschylus says—

They pour'd the water in a three-legg'd bowl,

Which always has its place upon the fire:

and the other is what is also called κρατὴρ, goblet. Homer says—

And seven fireless tripods.

And in these last they mixed wine; and it is this last tripod that is the tripod of truth; and it is considered appropriate to Apollo, because of the truth of his prophetic art; and to Bacchus, because of the truth which people speak when drunk. And Semus the Delian says—

A brazen tripod, not the Pythian one, but that which they now call a bowl. And of these bowls some were never put on the fire, and men mixed their wine in them; and the others held water for baths, and in them they warmed the water, putting them on the fire; and of these some had ears, and having their bottom supported by three feet they were called tripods.

Ephippus says somewhere or other—

A. That load of wine makes you a chatterer.

B. That's why they say that drunken men speak truth.

And Antiphanes writes—

There are only two secrets a man cannot keep,

One when he's in love, t' other when he's drunk deep:

For these facts are so proved by his tongue or his eyes,

That we see it more plainly the more he denies.