This Guy Drew a Cat. You Won’t Believe What Happened 4 Centuries Later.

Franz Helm’s illustrated manual on pyrotechnic weapons was around for more than four centuries before it went viral.

When the German artillery expert wrote the manual, in the mid-1500s, he unwittingly created a piece of media ideally suited to the tastes of 21st-century Internet culture: Cats that appeared to be wearing jet packs.

Helm appears to have been describing a creative siege tactic. In order “to set fire to a castle or city which you can’t get at otherwise,” he advised in the manuscript, an invading army might arm cats (and birds) with flammable payloads and then send the animals to wreak havoc inside the enemy’s walls.

Courtesy of U. of Pennsylvania

A version of the illustrations in Helm’s book, created as part of a digitization project at the University of Pennsylvania, went viral on the web last year. This month it went viral again, after an Associated Press reporter revisited the drawings. And this time around, delighted Twitter users began appending their posts with the hash tag “#rocketcats.”

The recent popularity of Helm’s obscure manuscript has left archivists, at Penn and elsewhere, wondering what this new form of public engagement could mean.

Buzzfeed, the web-culture omnibus site, published an article in February titled “8 Book Historians, Curators, Specialists, and Librarians Who Are Killing It Online.” The author, a former research curator at the New York Public Library, praised an array of academics “who embrace social media to broadcast their ardor for archival treasures.”

What is it worth to be “killing it online”? Should the stewards of university collections try to deploy rocket cats (and other “shareable content”) to reach audiences they couldn’t get at otherwise? Or would such a tactic be silly and ineffective?

Mitch Fraas, special-collections scholar-in-residence at Penn’s libraries, is among those killing it online, according to Buzzfeed. He was also instrumental in igniting the public interest in the rocket-cat illustrations.

In an interview with The Chronicle, Mr. Fraas seemed nearly as amused by the reaction to the rocket cats as others are by the illustrations themselves. Helm’s artillery manual has been in Penn’s collection since the 1930s or 40s, said Mr. Fraas. Strictly speaking, rocket cats are not a new discovery.

Still, there was some hope that the rocket cats might be useful ambassadors for the university’s online archive. “Come for the rocket cats, stay for manuscript culture in the early-modern period,” joked Mr. Fraas, brainstorming a promotional tagline.

Penn’s library blog did see a traffic spike last week, after the rocket cats caught fire for a second time. But less than 5 percent of visitors to the blog clicked through to the university’s digital-manuscript repository, according to Mr. Fraas. Seeing people post rocket cats on Twitter and Pinterest has been nice, he said, but “maybe 90 percent of the time they’re doing it unreflectively.”

Perhaps many of the people who hopped on the #rocketcats bandwagon merely chuckled, retweeted, and moved on.

And yet there is no denying that the new interest in the rocket cats has been educational. In 2013, after Helm’s book first got attention from Internet gawkers, Mr. Fraas was inspired to do some further digging into the university’s archives. He found another rocket cat in a different weapons manuscript. Someone on Twitter directed him to a third example. A sweep of the secondary literature yielded evidence of rocket cats, and rocket birds, in Asia, Russia, and Scandinavia.

Mr. Fraas summarized his findings in a blog post last year. That post drew attention from The Atlantic, which then published its own piece about the rocket cats. This year, the Associate Press’s retread inspired a more detailed—and better animated—essay on animal-borne instruments of war (e.g., surveillance pigeons and camel-mounted guns) by Benjamin Breen, a doctoral student at the University of Texas at Austin.

The argument that Twitter can bear only lightweight engagement with historical artifacts ignores an important point: Scholars and journalists live on the Internet like everybody else, and sometimes a small spark can ignite larger fires.