[kyuudou]

Later humans in Japan did using onsen, which is basically the same thing IIRC: http://www.bbc.com/travel/story/20200824-the-japanese-villag...

Definitely plausible.

[moufestaphio]

I've tried the 温泉卵 onsen tamago(https://en.wikipedia.org/wiki/Onsen_tamago). The one I had was kind of over cooked and had a sulfur taste. Wasn't great.

In Iceland they also use the hotsprings to cook bread: https://www.youtube.com/watch?v=vz-7iUw8Sl0

[eru]

Well, whether your egg will have a sulphuric taste will depend on whether the onsen you went to had sulphuric water.

[ipsum2]

No, just cooking an egg for a long time at high temperatures will bring out the sulfur taste. Try boiling an egg for 15 minutes.

[eru]

Oh, true, I hadn't thought about that.

[tdeck]

In Iceland they bury bread dough in little boxes near hot springs and bake sulfur-flavored rye bread

https://en.wikipedia.org/wiki/R%C3%BAgbrau%C3%B0?wprov=sfla1