Ars longa, Vita brevis WoO 193 (1825)
No doubt Beethoven jotted down this canon with tongue in cheek, because he's cheating here: all the notes of the melody belong to the tonic triad, which means it can be combined in any way you want without ever creating any harmonic roughness. It is worked out here for five voices, but it could just as easily be worked out for 10 voices. That, however, wouldn't make this canon any smarter. It's better to just smile at Beethoven's chaff.
The words "Ars longa, vita brevis" ("Art lasts long, life is short") are depicted in the music: "Ars longa" has long notes, "vita brevis" short notes.