First, the adumbrations of one of Penn’s crack librarians (historians?), Mitch Frass, on the codex, its probable source (turns out it is a copy of an earlier book of “proven arts” by a chemist/artillery-master/maybe-alchemist named Franz Helm), and the circumstances that led to many very similar versions being distributed around Europe over two plus centuries. Helm explained the fire-cat and fire-bird as follows:
So what does Helm actually say about these explosive animals? Are there rockets involved at all? In the text accompanying the images is a section entitled “To set fire to a castle or city which you can’t get at otherwise” . This section details how to use doves and cats loaded with flammable devices to set fire to enemy positions. On cats the text paints a grisly picture of attaching lit sacks of incendiaries onto the animals to have them return to their homes and set fire to them. In my awkward translation:
“Create a small sack like a fire-arrow … if you would like to get at a town or castle, seek to obtain a cat from that place. And bind the sack to the back of the cat, ignite it, let it glow well and thereafter let the cat go, so it runs to the nearest castle or town, and out of fear it thinks to hide itself where it ends up in barn hay or straw it will be ignited.” 
There’s no way to know if Helm himself ever employed this method of pyrotechnic warfare but strangely enough the idea of using cats and birds in just this way appears in historical texts from many disparate regions of the world. In a magisterial article on the subject, the Finnish scholar Pentti Aalto cites examples of incendiary-bearing cats and birds from a 3rd c. BCE Sanskrit text, the Russian Primary Chronicle, early Scandinavian sources, and an early modern history of Genghis Khan .
A bit hard on the cat, but all you guys who still cling to your 1980s-vintage copy of 101 Uses for a Dead Cat will find it worth pursuing, perhaps. Not to mention all you doomsday preppers. Hey, if it worked in 200-something BC, and was still worth writing up in the 16th Century, it will work when the grid goes down, right? Anyway, the whole of the post on the history of Codex 109 and its cousins is worth reading at length, and the cat illustrations are unintentionally hilarious, so go Read The Whole Thing™.
You will recall that we mentioned in the AM post that Penn’s librarians had suspected that Codex 109 might have been a manuscript copy of the Feuerwerkbuch in the Staatsbibliothek in Berlin. As it happens, Helm’s book embraces and extends the 1420-vintage FWB (the ur-manuscript of which is apparently lost, the Berlin copy being, perhaps, a 1st-generation ms copy). But someone has transcribed the Feuerwerkbuch based on the Berlin manuscript and several others, and even better, translated it into modern German and set up a site hosting these files.
At that site you will find some remarks (in German and in English) and several downloadable .pdf files, one containing meta-information, one a synoptic copy of two versions of the text (rendered in the original Early New High German but with modern letters), with many explanatory remarks, and one the complete text translated into current High German.
Finally, Alexis Madrigal, whose notice brought it to our attention i the first place, followed up himself. We missed his follow-up until we saw that Mitch Frass at Penn caught it. Sorry, Alexis.
Thanks again to the WeaponsMan.com reader who brought this to our attention.