How did mercury’s high density make it useful in barometers and manometers?

Mercury’s high density was essential for the design of barometers and manometers because it allowed these instruments to be built to a manageable, practical size.12

Because atmospheric pressure is significant, a liquid with low density—such as water—would require a very tall column to balance it; for instance, a water-based barometer would need to be approximately 10 meters (34 feet) high. In contrast, because mercury is about 13.5 times as dense as water, a mercury column only needs to be about 76 centimeters (30 inches) tall to balance the same atmospheric pressure at sea level. This compact size enabled scientists like Evangelista Torricelli to conduct experiments easily and allowed for the development of portable and functional measuring devices.32

While mercury was historically favored for these instruments due to its density and low vapour pressure, its use has been largely phased out in many regions due to the metal's toxicity.31