We all know the benefits of units in Mathcad, and the Mars Climate Orbiter and the Gimli Glider have been cited numerous times on the forums as examples of why units matter. Here's a couple of lesser known ones though:
The Vasa warship:
In 1628, crowds in Sweden watched in horror as a new warship, Vasa, sank less than a mile into her maiden voyage, with the death of 30 people on board. Armed with 64 bronze cannons, it was considered by some to be the most powerful warship in the world. Experts who have studied it since it was raised in 1961 say it is asymmetrical, being thicker on the port side than the starboard side. One reason for this could be that the workmen were using different systems of measurement. Archaeologists have found four rulers used by the workmen who built the ship. Two were calibrated in Swedish feet, which had 12 inches, while the other two measured Amsterdam feet, which had 11 inches.
Stonehenge model:
In the 1984 mockumentary This is Spinal Tap, the members of a fictional rock group order a model of a Stonehenge megalith for their stage show - but the note written on a napkin mistakenly asks for a model 18 inches tall, instead of 18 feet. Curiously, and probably coincidentally, the British rock band Black Sabbath had experienced the opposite problem during its Born Again tour in 1983. Its replica of Stonehenge was so big, it got in the way of the band, and very few of the "stones" would fit on the stage. One version of the story says there was a mix-up between metres and feet.
Both courtesy of the BBC: http://www.bbc.com/news/magazine-27509559
Why don't we have "Amsterdam feet" as a unit in Mathcad?