To create the metric system back in 1792, Pierre-Francois-Andre-Mechain and Jean-Baptiste-Joseph Delambre officially detemined length of a meter. They set it at one ten-millionth of the Earth’s meridian.

But how to measure the meridian? Glad you asked. The two men spent a mind-boggling seven years measuring out a precisely straight line from Dunkirk to Barcelona, so that they could triangulate the entire meridian from this smaller chunk.

Simple? Hardly. In practice this meant clambering to the summits of mountains, or punching holes in church steeples, or hammering together scaffolding in the middle of forests, raising pyramids or reflectors, and sighting them from dozens of miles away with a telescope. Two guys burn lanterns on two mountaintops; another guy travels 60 miles, climbs his own mountaintop, and takes readings all night to measure the angle between the two. Repeat. For seven years.

The obstacles they faced were awesome: marauding citizens bent on beheading, chronic funding shortfalls, loose screws on their instruments, jealous colleagues. Villagers accuse them of being sorcerers. Volunteer brigades quarantine them in town halls. Now mix in the fact that Mechain so devoted himself to exactitude that a possible error in his calculations drives him to the brink of insanity, and [the] story really picks up. Obsession, guilt, ambition; the psychological costs of utter precision.

The story’s told in a new book by Ken Adler, The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World. Excellent review of it at the Boston Globe. Damn, I want to read this.