What about chants? They don't have a standard meter. I'm not sure if that's what you were thinking of though.
Reicha's 36 fugues (forget the exact date but about the time Beethoven popped his clogs) include various off time signatures and all kinds of other zaniness, and most people, hearing them, will confidently guess a date of composition betwen 50 and 100 years after the time of their composition. STRONGLY RECOMMENDED REPERTOIRE!