Moving the lever of the red velvet seat causes the quill to move erratically along the horizontal plane.
The tome appears to have writing on other pages, all in enormous letters, but you cannot read the words as they have been blotted out. A word or two is all that will fit on a page spread.
The lever does not seem to affect the mirror, but from the high seat you can see two horizontal iron rods on swivels attached to the sides of the mirrors.