Galileo’s thermoscope, developed in the context of pneumatic engineering, was an ancestor to the thermometer. Galileo pioneered scientific investigations with the thermoscope along with his two Paduan friends, Giovanni Sagredo and Santorio Santorio. Santorio affixed measuring units to the glass tube. Sagredo attempted to standardize the scale to correspond to the temperature of snow, of salt water on a cold day, and of the hottest day of summer. Sagredo used a thermoscope to refute the common belief that well water is warmer in the winter than the summer, finding that it was actually colder, although it feels warmer to our senses.