In the northern part of the world near the library/telescope area past the pink hub and off to the east is a purple room with a couple of those block pairs that close to flatten and kill you once you jump on them. You'll need to jump on them and shift the world to avoid getting squashed while also using the lift momentum to reach the higher parts of the stage.
At the top is a door leading to more library rooms. Along the way you'll have to reveal a hidden door by pushing a bookcase in a small room with the X-button. Eventually three short rooms in you'll find a giant globe that the hypercube remarks can be rotated. Spin the globe around until it reveals a door. Enter the door, and you'll find a chest with this artifact inside.