The mineral ingredients may be hard to achieve, but maybe we can find supplemental additives? For sure the warmth above 92 degrees has it's benefits.
One of my early memories is the bath house on my Grandfather's brother's farm. They all worked out in the field from sunrise to sunset, but Auntie came home early and lit the fire under the converted metal horse drinking tub - filled with water situated over a firebox, enclosed in a 6' x 6' shed. Then she went into the house to cook dinner.
There is a proper order of the man of the family first, then the children - boys first - then the mother. We scrub up outside the tub, rinse off and then sit in the tub, sitting on a bench and a wood lathed foot area.
I want a Donabe (ceramic pan) for Christmas so I can make some of what they say is the most wonderful tasting rice ever.