Fahrenheit is a temperature scale based on one proposed in 1724 by the German physicist Daniel Gabriel Fahrenheit (1686–1736), after whom the scale is named. It uses the degree Fahrenheit (symbol °F) as the unit. There exist several accounts of how he originally defined his scale. The lower defining point, 0 degrees, was established as the temperature of a solution of brine made from equal parts of ice and salt. Further limits were established as the melting point of ice (32 degrees) and his best estimate of the average human body temperature (96 degrees, about 2.5 degrees less than modern measurements). The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 degrees, and the boiling point of water is defined to be 212 degrees, a 180-degree separation, as defined at sea level and standard atmospheric pressure.