The invention of liquid thermometers was inspired by the human body. The picture below shows an example liquid thermometer.
There is a reservoir of liquid at the bottom of the thermometer.
That liquid will raise and lower to different heights within the tube above the reservoir,
depending on the temperature.
The most obvious inspiration from the human body is the male sex organ.
A thermometer looks like a male sex organ.
The mercury reservoir bulb at the bottom of the thermometer looks like the scrotum.
The glass column above the reservoir looks like the shaft of the penis above the scrotum.
The thermometer would have been based on the concept that when the penis is sexually stimulated or “hot”, it rises upwards.
The second inspiration from the human body also involves the sex organs.
Sexual stimulation can cause two areas of the back on either side of the spine,
to “rise up” in the same way that the penis rises up when it is stimulated. When these areas on the back are not being sexually stimulated, they shrink or lower the same way a penis shrinks or lowers.
The scrotum again plays the part of the mercury bulb in this example,
with the two areas on the back behaving like fluid rising up the straight section of a thermometer.