Used mostly in the 19th century, Cross-writing is a technique for saving paper. After a page of writing or after both sides of a page were filled in, the writer would then turn the page 90 degrees and continued writing, adding a second layer of text, perpendicular to the first. Apparantly it is surprisingly quite easy to read, as a reader's mind naturally tunes out the irrelevant lines. Via BMD Love Blog (Bruce Mau Design).
