The above is an introduction. Filipovic's research has featured in Atlantic Monthly magazine. Research not on papal bulls, but business documents. Here is what the magazine says.
Now, via medievalist Emir O. Filipovic, evidence that cats have been up to .... mischief for six centuries: inky pawprints, gracing a page of the 13th volume of "Lettere e commissioni di Levante," which collated copies of letters and instructions that the Dubrovnik/Ragusan government sent to its merchants and envoys throughout southeastern Europe (Bosnia, Serbia, Croatia etc.), according to Filipovic -- sort of a 15th-century Federal Register. The particular document that the cat got its paws on dates to March 11th, 1445.
And here is the evidence, a path across a page, a continent, a globe, and six centuries:
A cat got its paws wet, possibly by trotting across freshly inked documents, and left a path of paw prints in a book constructed before the printing press was invented. Like a trail in the snow, only this white lasted longer than one winter. Ou sont les neiges d'antan. They are above.