I was just listening to the La Sagrada Familia episode of 99% Invisible last night where the talk about this exact thing. It's a really good episode if you want more insight into this.
The catenary arch, and this construction method, has an
interesting history:
>In 1671, Hooke announced to the Royal Society that he had solved the problem of the optimal shape of an arch, and in 1675 published an encrypted solution as a Latin anagram[10] in an appendix to his Description of Helioscopes,[11] where he wrote that he had found "a true mathematical and mechanical form of all manner of Arches for Building." He did not publish the solution to this anagram[12] in his lifetime, but in 1705 his executor provided it as ut pendet continuum flexile, sic stabit contiguum rigidum inversum, meaning "As hangs a flexible cable so, inverted, stand the touching pieces of an arch."
Hooke was fond of publishing his ideas as ciphers. Ideas in his time were often discovered simultaneously in many places at once, and so I think the purpose was not to convey the solution, but to provide a sort of proof-of-work that he had found a solution without letting anyone else take credit for it. I guess he expected the answer to be discovered somewhere else fairly soon thereafter, maybe by one of his colleagues, at which point he could unscramble the anagram and say "see, I beat you to it".
Heh; I didn't know about this practice! This is amazing, sort of a proto-"posting a shasum to Twitter so you can say 'I KNEW IT' at some point in the future".
