A great Wikipedia nugget just discovered:

It was also at this Council [of Constance, 1415-19] that a cardinal ventured to correct [Emperor] Sigismund’s Latin (he had construed the word schisma as feminine rather than neuter). To this Sigismund replied: “I am king of the Romans and above grammar.”

This is almost as good as another quip, from Ferdinand I of Austria (r. 1835-1848), who is:

best remembered for his one coherent command, to his cook when told he could not have apricot dumplings (Marillenkn√∂del) because apricots were out of season. He said “I am the Emperor, and I want dumplings!”