Question: What was the boiling point of water on the original Celsius centigrade thermometer?
Answer: The first Celsius thermometer set water’s boiling point at 0 degrees, with freezing set at 100. That seems completely backward to us, and not long after the death of its inventor, Anders Celsius, in 1744, his thermometer was reversed to its current form, where 0 represents freezing and 100 means boiling. Celsius originally set freezing at 100 to avoid having to use negative numbers for sub-freezing temperatures (instead, sub-freezing temperatures would be numbers below 100).
