King Sejong. For the poor, Buddhist monks ran sweat-steaming houses: domes of stone and clay, a pine fire inside, then water, then steam. The sick lay on pine needles, wrapped in straw. But the monks had one method for everybody. They did not ask what was wrong. They made everyone sweat. And sometimes a patient died.

So the court decided: two physicians at every sweat-house. First, examine the patient. Sweat only those who are fit to sweat. If someone is harmed, doctor and monk will both be punished. Six hundred years ago, maybe the first sauna safety rule in history.

Five years later the monks wrote back. The sweat-houses worked, cures without end, but the poor could not pay for firewood, salt or soy sauce. So the state gave rice and cloth to live on the interest.

Today Korea has the jjimjilbang, open all night, eggs included. And the oldest rule still stands: not everybody should sweat the same. Not even Finns.

How do you know when you have had enough heat?

Sources: Annals of the Joseon Dynasty (Sejong sillok), entries of 1422 and 1427, our translation from the classical Chinese; Encyclopedia of Korean Culture, "Hanjeung" (Kim Shin-geun, 1995); Sillok Wiki, "Hanjeungso".
Sounds: Freesound (CC0): kerozenne, bassimat, thedapperdan, Reitanna, soundandmelodies, zembacraftworks, santiagogra. Forest recording: Yle Arkisto, CC BY 4.0.