ricardienne | Commonplace Book: Aeneas Tacticus on Secret Messages

One of the problems with fantasy novels is that when you use magic for things like, say, encoding secret messages so that they look innocuous to anyone but their intended recipient, you take a lot of the potential fun out of it. Here are just three of the many examples of ways to send secret messages provided by Aeneas Tacticus (c. 4th/3rd century BCE?):

Send a man bearing a message or a letter about something unconcealed. When he is getting ready to set out, secretly put a message inside the soles of his sandals and sew them back up. (In case of mud or water, you should engrave it lightly on tin to provide against the letters vanishing because of the wet). When he arrives at the appropriate person and has gone to sleep, the recipient undoes the seams of his sandals, takes out the letter and reads it, writes another secretly while he is still sleeping, and, sewing it back up, sends the man back either to report or with another unconcealed letter. This way, no one else, and not even the bearer himself, will know. But you must make the stitching on the sandels as invisible as possible.

A letter was brought to Ephesus in the following manner. A man was sent with a letter written on leaves, and the leaves were bound into a poultice upon a wound on his leg.

A letter could also be sent via a woman's ears, if, instead of earings, she wore thin lead plates rolled up.
Aeneas Tacticus, "How to Survive A Siege", 31.4-7.