magic compass messages

I really enjoyed the beginning of How to Send a Secret Message from Rome to Paris in the Early Modern Period: Telegraphy between Magnetism, Sympathy, and Charlatanry, which describes a sixteenth-century scheme to send secret messages via magically linked compasses. It's part of a special issue on early modern concepts of action at a distance (many of the articles are open access). It's really interesting to watch the way the boundaries of what counts as science changed.