Well, then, here's a real knee-slapper of a riddle that's CERTAINLY mature (if mature means "old enough to know better"):

Wrætlic hongað bi weres þeo,        
frean under sceate. Foran is þyrel.
Bið stiþ ond heard, stede hafað godne;
þonne se esne his agen hrægl
ofer cneo hefeð, wile þæt cuþe hol
mid his hangellan heafde gretan
þæt he efenlang ær oft gefylde.