Latino sine flexione

Also known as Peano’s Interlingua (not to be confused with the IALA’s 1951 Interlingua), Latino sine flexione was a conlang released in 1903. The contention of its creator was that the world didn’t really need a new international auxiliary language, because we already had Latin. All that needed to be done was simplify the grammar a bit to make it easier to learn for people who don’t speak such highly-inflected languages as Latin is; Latino sine flexione was the result.