Writing in code

When mail first became available to everyone in the 17th century, postage was paid by the person receiving the letter. Cost depended on the number of pages sent, and the distance they travelled.

If you had very little disposable income, you might dread the arrival of the postman. People went to great lengths to avoid paying their dues. Some would write cross-ways several times on the same sheet - harder to read, but cheaper to send. Some even concealed messages on the cover. In this latter case you could see the message, then hand the letter back without paying.