[TigersEye]

Are they saying that the cauldron still had 3.7 gallons of liquid in it?

If so that was one heck of a vessel and the stopper must have been amazing.

[SunkenCiv]

[snip] In the Celtic legend of Bran the Blessed, the cauldron appears as a vessel of wisdom and rebirth. Bran, mighty warrior-god, obtains a magical cauldron from Cerridwen (in disguise as a giantess) who had been expelled from a lake in Ireland, which represents the Otherworld of Celtic lore. The cauldron can resurrect the corpse of dead warriors placed inside it (this scene is believed to be depicted on the Gundestrup Cauldron). Bran gives his sister Branwen and her new husband Math — the King of Ireland — the cauldron as a wedding gift, but when war breaks out Bran sets out to take the valuable gift back. He is accompanied by a band of a loyal knights with him, but only seven return home. [/snip]

https://www.learnreligions.com/cerridwen-keeper-of-the-cauldron-2561960

[Harmless Teddy Bear]

Residue only I am afraid. But I find the meadowsweet and mint interesting. Mint helps with stomach upset and meadowsweet does as well along containing salicylic acid.

It could be that this was at least partly a hangover remedy.

A bit of hair of the dog in case waking up in the next world is somewhat rocky.