Rongorongo

Wooden tablets from Rapa Nui covered in rows of tiny carved glyphs, and the only writing system ever developed in Polynesia, probably invented on the island itself no earlier than the thirteenth century. You read it in reversed boustrophedon: start at the bottom left, read left to right, then turn the tablet 180 degrees and carry on. About 26 authenticated pieces survive, roughly half in good condition, and not one of them is on Rapa Nui. They are in Rome, Vienna, Berlin, London, Paris, Santiago, St Petersburg, Washington and Honolulu. Eugène Eyraud saw hundreds of tablets in 1864; by 1868 there were a few, because the Peruvian slave raids of 1862 had taken the population and with it everyone who could read, and the tablets left behind got used as fishing-line reels and firewood. Some calendar and possibly genealogical structure has been identified. Not a single glyph can be read.