EVERYONE SAYS that the great 40" refractor at Yerkes Observatory is the world’s largest, but did you know that there was actually a larger refractor built in France? It was on display at the Paris Universal Exhibition of 1900 and had an objective of 49.2 inches. The optical tube was mounted horizontally and fed by a 79-inch flat mirror which tracked the sky. A handful of scientific observations were made with the telescope during the Exhibition, but no buyer was ever found for it. Ultimately the instrument was scrapped.
Fast forward approximately 100 years: recently some of the optics from this scope were found in storage in the basement of the Observatoire de Paris, and the flat mirror is currently on display there.