At the beginning 0f his poem John Shade (the poet in VN's novel Pale Fire, 1962) mentions that crystal land outside the window:
I was the shadow of the waxwing slain
By the false azure in the windowpane;
I was the smudge of ashen fluff - and I
Lived on, flew on, in the reflected sky.
And from the inside, too, I'd duplicate
Myself, my lamp, an apple on a plate:
Uncurtaining the night, I'd let dark glass
Hang all the furniture above the grass,
And how delightful when a fall of snow