Thanks to
terri_testing, I've been re-reading
Jodel's essay on Wizard/Muggle relations, and a thought shook loose on how wizards might have gone about finding Muggleborns before the Hogwarts Quill came into operation.
We don't know exactly when that was. It could have been the 18th century, purely because when you see people scratching away with quills in the movies, it's so often those guys in wigs and stockings. But take your pick from between the 6th and 19th centuries. (Did you know the U.S. Supreme Court
still hands out quill pens to lawyers as souvenirs? I didn't! I guess we can't get on the Brits' case too much about the wigs.)
Because many of the magical discoveries we know of come in the 13th century (Floo powder) or later - and while they did invent things in medieval times, the rate of discovery was slower than in later centuries - for the sake of argument, let's say the Quill was invented some time after that. While they probably wouldn't want untrained magical kids running around causing who-knows-what troubles in any era, due to the small population, it probably was not a really pressing need until the major witch hunts of the 15th through 17th centuries and the imposition of the International Statute of Secrecy in 1689/92. (I mean, it's maybe two unidentified kids who occasionally accidentally blow something up. Not such a big deal.) So I'll date it to, say, the first few decades of the 18th century, and we can have our bewigged wizards consulting with Dilys Derwent over at St. Mungo's on figuring out a better way to locate these kids. (And then she became Headmaster, watching over the kids she'd helped identify. Very neat.)
But how did they locate the occasional Muggleborn before that, if they did?
Jodel has some good suggestions in her essay. Local priests might notice and take the kids into the church (and if there were any wizarding priests around, give them some magical instruction or send them off to Hogwarts). Wizarding "great houses" who found one in their regions of influence (probably an unacknowledged cousin of some sort anyway) might sponsor their training.
I'd like to add another possibility, closely related to the first:
We know that the Hufflepuff House ghost is the Fat Friar. For years, I saw that and thought, oh, look, there's confirmation that sometimes wizards did have a vocation, and that was the end of it.
But the thing about friars is, they are not cloistered or even as closely tied down as a parish priest, who usually served an area roughly corresponding to a township or great estate. A friar is a member of one of the mendicant orders which got going around the 13th century - and their deal is to wander around in whatever province or county they have chosen or been assigned, begging for sustenance and serving the spiritual needs of everyone in the area. Of course, this is not always what happened in practice. Nevertheless... doesn't that sound convenient for wizards? A wizard friar could move from town to town in his county, getting to know all the local gossip, and so would have a better chance of hearing about children who did "odd" or "miraculous" things than someone who stayed put. He would also be able to find out and intervene if a parish priest who had discovered one of those "odd" children was more inclined to think it demonic than miraculous. And of course, he would have an excellent excuse if anyone heard him muttering funny words in Latin and performing small miracles.
Any Muggleborn children discovered this way could then be sent off to Hogwarts, under the cover story that they were obviously very holy children and just had to go to Whatsit Abbey for proper religious instruction. (For that matter, just because we don't see it happening now doesn't mean Hogwarts never offered religious instruction. They were all theoretically Catholic for about half of its existence, and the early universities founded a little after Hogwarts were all kinds of mixed up with the church - Oxbridge fellows were supposed to be ordained priests right up until the 19th century, iirc.) Just as the children discovered by a great house might then owe them a debt as retainers of some sort, these children might owe the wizarding members of the church, and eventually would be encouraged to join a mendicant order themselves to pay it forward, as it were. (They could get married and have lots of magical babies first - no hurry. For that matter, wizards might have had different opinions on clerical celibacy, which took a while to get established anyway and was, er, not so strictly followed as some might have wished.) The Fat Friar may in fact be one of these cases, who went so far as to stay on as a ghost watching over his House's children when he was no longer able to wander around like a living person. Although actually we don't know any reason he couldn't have carried right on wandering, unseen by Muggles, until the Quill went into operation and this particular services was no longer needed, after which time he stayed at Hogwarts.