During the 19th century, mercury thermometers were big, measuring at least a foot long. It needed at least twenty minutes to accurately measure a person’s body temperature. In 1867, Sir Thomas Clifford Allbutt devised a smaller mercury thermometer measuring six inches long. It only needed five minutes to accurately measure a person’s body temperature.




In 1990s, production of mercury thermometers was discontinued. It was no longer recommended for medical use as it was too dangerous to handle. The vigorous swinging needed to reset the mercury level inside the thermometer could lead to accidental breakage resulting in poisonous mercury exposure.