On my recent trip to Belgium I went to the Antwerp Museum of Fashion, MOMU for a fascinating exhibition on the paper dress. It doesn't sound desperately relevant to a crochet blog but you would be surprised!! Displayed were 19th centuryJapanese Samurai underwear (yes, even they need knickers!!!) made from knotted paper. As you can imagine it was the knotted stitch they used that caught my attention.
The Solomon's knot is as much macrame as crochet but students are still intrigued as to how to make the stitch. Created by lengthening a chain stitch and then crocheting into the back of the chain, this is a simple stitch and a lovely way to create an airy and open-work piece. But don't take my crass description as gospel. Nexstitch offers a very clear, visual tutorial of this and many other stitches.
It has been popular for use in quite utilitarian items (such as underwear) and bags and this little pouch from the 1920's is a lovely example.