1796: Old Japanese with Chinese Word Order
Japanese orthography may be the hardest in the world to learn. Partly since it uses 3 different writing systems today, but, Old Japanese was even harder, because it used only Chinese characters and also word order. However, Chinese is written subject-verb-object and Japanese is subject-object-verb, so while keeping the Chinese word order, Japanese writers would have to note the way in which the words were ordered with other special symbols.
For more on diglossia, click here.