Here are two 19th Century “cross written” letters. Cross writing was a technique to save paper when paper was scarce. Every scrap mattered at one time (one of these is dated 1823) so the writer, upon reaching the end of the page,
would turn the paper 90 degrees and add a second layer of text. Once it
becomes familiar, the mind adapts easily and cross written letters are
surprisingly legible. Charles Darwin famously used the technique.
A Florida woman used the comments section of a Pizza Hut order made from her smartphone to alert authorities that she and her children were being held hostage. When police responded to her message, arriving at the location, she and her children were quickly released, unharmed, and the kidnapper was arrested. [x]