Before the first real thermometer was invented they had things called thermoscopes that didn't give you an exact temperature but gave you an idea hot and cold. The closest thing to a thermometer was "Galileo's Thermometer" technically still a thermoscope, but it used marked bulbs that had different masses. The bulbs would either sink or float and the lowest bulb told you the temperature.
There were lots of different thermometers made around the same time period like the first practical medical thermometer made by Sir Thomas Allbutt, the first ear thermometer made by Theodore Hannes Benzinger, and a lot more.
The first air and liquid thermometers were made possible by using Lord Kelvin's "Kelvin Scale" which was one of the first measuring scales for temperature to actually get an accurate temperature reading.