Carl Linnaeus, The Lapland Journey, translated by Peter Graves (Edinburgh: Lockharton Press, 1995), p. 192.

Northern Husbandry, 24/09/1732, ¶1124:

Between Midsummer and the Feast of St James, they take the whey after cheese has been made and boil it for a few hours. When it has cooled, it is put into a cask and kept for the winter. Poor old women beg or buy small bottles of this during the winter. A 1/4 measure of this is added to a full measure of sourmilk and, when they are mixed, it tastes like soured milk.