Temperature measurements started with the developments of thermoscopes and thermometers. They were based on the fact that liquids in general expanded significantly on change in temperature (especially mercury). The initial mercury thermometers were calibrated against common physical phenomenon and divided linearly (for example, the Celcius scale).
But now we know that materials do not expand linearly with temperature. How was this knowledge incorporated to get a material independent temperature scale, because if we continued using a linear scale we would face problems at high temperatures?