Some people have said that an eye is a window, but anyone who has looked carefully has seen that an eye is a mirror.

[...]

I put Tess of the D’Urbervilles back in its place on my shelves, and I took down Wuthering Heights and looked at certain pages. At first I looked as though I was looking through window-pages, but then I saw that the young woman I saw was not even a young woman but a girl-woman and that the grassy place I saw was not a moorland but part of a paddock of grass in the district between the Moonee Ponds and the Merri. When I had seen this I was ready to acknowledge that a page of a book is not a window but a mirror. But in order to prove this finally to myself I looked for a certain page that I remembered in Wuthering Heights. The words on that page describe a man sleeping in a room and dreaming of the ghost of a female child who is trying to get into the room from outside by way of the window.

I stood in this room of my own and I held out in front of me the page where the word window is printed. If a page of a book is a window, I should have seen at that moment – in order from the nearest to my eyes to the furthest from them – the man in his room, the window of that room, and on the other side of that window the face of a female child calling herself Catherine Linton. I should have seen, while I went on looking at the page which was itself a window and which had the word window printed on it, the man thrusting his fist through the glass from inside outwards, then the female child gripping the man’s hand with one of her own hands, then the man trying to shake his hand free from the grip of the hand of the female child, then the man dragging the wrist of the female child backwards and forwards across the edge of the broken pane until the wrist is marked by a red circle of blood.

But what I saw instead was myself in the room and a girl-woman on the other side of the window and trying to get in. I was a man whose hair had turned grey at its edges and whose belly had begun to protrude. The girl-woman was someone I had last seen when she and I were twelve years old. And I did not thrust my fist through the glass; I turned a key in one of the double panes of the window and swung the panes apart and then back against the walls of the room. Then I took hold of the wrist of the girl-woman and guided her into the room.

I had believed for most of my life that a page of a book is a window. Then I had learned that a page of a book is a mirror. (Inland)