Accusative ad curiam si ceperis ire,
Proficis in nichilo, si pergis absque dativo.
The “nichilo” is a medieval spelling of “nihilo”, which shows us that they pronounced that “h” in late-13th-century Italy. (Or wherever and whenever that guy he was quoting lived, but I figure Salimbene would have changed the spelling to something he was comfortable with; they weren’t so punctilious about that stuff then.)
This means, basically:
If you get the idea to go to court accusatively,
You won’t succeed in anything if you proceed without the dative.
In other medieval Latin humor, around the same time, Pope Boniface VIII was talking to one of his cardinals, Jean Lemoine, who was advising that he should cancel some grants made by his predecessor because they were made without consultation by the cardinals. Of course Popes didn’t like it when cardinals suggested that Popes had to consult with them to act legitimately. Boniface VIII ended up canceling the grants, but first he blew up at Jean Lemoine, who was from Picardy:
Picharde Picharde tu habes caput Pichardicum, sed per Deum ego piccabo te, & faciam in omnibus velle meum, & non dimittam pro te neque pro omnibus qui estis hic, sicut pro asinis.
This basically means:
Picard, Picard, you Picard-head, by God, I’m going to pike you, and I’ll do what I want in all things, and I won’t cancel [those grants], for you nor for all the other[ cardinals] here, as I wouldn’t for asses.