Lewis Carroll’s ninth rule of letter writing was to never cross your letters. But many people did it anyway.
The concept of a crossed letter is pretty simple. Write whatever you have to say, and once you run out of room turn the page sideways and keep writing. The cross-hatched words remain surprisingly legible, and you’ve halved the amount of paper needed. (People were always looking for ways to save money on postage.) The English Romantic poet John Keats was a fan; so was Jane Austen.
Lewis Carroll was not a fan. He wrote a little essay about the etiquette of writing letters, and his ninth rule specifically calls out crossing:
9th Rule. When you get to the end of a notesheet, and find you have more to say, take another piece of paper—a whole sheet, or a scrap, as the case may demand: but whatever you do, don’t cross! Remember the old proverb Cross-writing makes cross reading.
Carroll’s rules are actually a pretty good guide to communicating on the Internet, by the way. Consider the following rules:
7th Rule. If it should ever occur to you to write, jestingly, in dispraise of your friend, be sure you exaggerate enough to make the jesting obvious: a word spoken in jest, but taken as earnest, may lead to very serious consequences.
4th Rule. When you have written a letter that you feel may possibly irritate your friend, however necessary you may have felt it to so express yourself, put it aside till the next day. Then read it over again, and fancy it addressed to yourself.
So Carroll was against both crossed letters and cross letters. Finally:
6th Rule. Don’t try to have the last word!
[Thanks to brushtailedphascogale for drawing my attention to this topic.]