Pure².

...Poor Lily, she only wanted to visit the hot springs.

Well, I did tried lumber-heated cast iron vats bathing with mildly sulfuric water from nearby stream. Example Yes, it really lacks devil with pitchfork nearby.
It was awesome - especially when you warm up to 40+ °C and jump in cold (single digit °C) stream, wait till cold reach bones and guts and then crawl back to cauldron.
If I ever get "any bath" wish to materialize - it'll be those cauldrons.