Remember that Medieval manuscript with the centuries-old pawprints? Today's proof that cats have always loved ruining things comes in the form of cat pee.
In 1420 a scribe in what is now the Netherlands discovered that a cat had urinated on a document he was working on. Instead of scrapping the work, he added an addendum to the piece, with some words of wisdom for future cat owners. While originally written in Latin, in English the text reads
Here is nothing missing, but a cat urinated on this during a certain night. Cursed be the pesty cat that urinated over this book during the night in Deventer and because of it many others [other cats] too. And beware well not to leave open books at night where cats can come.
Check out this 15th Century manuscript. Notice anything familiar? In totally-non-shocking-news-of-the-day, it turns out cats have been walking on whatever you're writing since the dawn of time. Emir O. Filipovic of the University of Sarajevo's History Department discovered the medieval kitty prints.
We can only assume that somewhere, beyond the reach of time, in a small ancient monastery in the mountains, the muffled sounds of "SNOWBALL, OFF. OFF. DOWN. GET DOWN, SNOWBALL. BAD KITTY. DAMNIT, SNOWBALL GO SOMEWHERE ELSE," carry across the medieval vales and valleys.