Blue Sky Zone, Waterfall screen
The first zone you should enter, rotate the screen until you find an exit leading you to the crying waterfall screen. Above the waterfall face is a tree which will take you to an off-shot room. In this room will be sparse but a solitary cube bit, some Fezian writing, and a chest that you can ascend to by navigating the mushrooms and rotating. The chest is what will contain the Writing Cube artifact, used in the past by the citizens of Zu for writing.