The year is 1851. Sociologist Eilert Sundt is walking across a field in Hedmark, central Norway, when he notices a pile of stones. They catch his eye because they look peculiar. They’re small, about the size of a fist, with obvious signs of burning, and they have been chipped and cracked somehow. He asks a farmer working nearby what the stones are.
“Brewing stones,” says the farmer.
“Yes, boiling stones.”
“Yes. They were used for boiling in the old days, when people didn’t have metal kettles.”
Eilert Sundt (Oslo Museum: image no. OB.03176 (Byhistorisk samling), via oslobilder.no, CC BY SA)