Rømer (°Rø)

A scale created by the Danish astronomer Ole Rømer in 1701, setting a brine freezing mixture at zero and body temperature near 22.5.

Rømer chose a brine mixture as his zero because it was the coldest temperature he could reliably reproduce in a laboratory, avoiding negative numbers in ordinary use. Daniel Gabriel Fahrenheit visited Rømer in Copenhagen in 1708, saw the method, and adapted it directly: the Fahrenheit scale is essentially Rømer multiplied by four and shifted, which is why Fahrenheit zero also sits at a brine freezing point rather than anywhere obviously meaningful.