@larand Yeah, Microsoft took quite much artistic liberties there. Google got closer, though Jaakko threw a stone from the stove of a sauna. I wonder from how did they come up with stomach there.
For the background, the waters are hottest, statistically speaking, on the day when it’s the name day of Jaakko. Hence, folklore saying that Jaakko throws a (cold) stone and the waters start cooling.
// @matigo