[He winces; it had been an offhand comment, but he'd made enough of those around people who cared about them to at least feel bad when he was called out on it.]

Yeah...yeah, they are.

[At least...well, he really, really hopes that they are. After a pause, though, he's back at the mystery, because that's better than getting mad at himself over something.]

What about optics? There's fibers that small, right? Well, maybe not. It's a hundred years ago.

Um, as far as tracking ,though. A little radio transmitter should be easy enough to find. Just put it in like a bookmark and follow the signal. Maybe tie something to the book, too, so you can spot it when you're close?