Michelle commented yesterday saying that she didn't quite understand the whole "through the viewfinder" thing and I realized, I didn't really explain it really well. Since there's like a million tutorials online, I'm not telling any secrets here. So, here's how I did it.
I started with my Kodak Duaflex IV. You can find these on eBay or at a vintage store or thrift store. I think my sister paid like $5 for this.
You will notice that there is glass on the top of the camera which is the viewfinder you look through to shoot the picture. I removed the cover from the viewfinder.
Then I took a cardboard box and cut it into strips and put it into another box held together by duct tape. I also put a shoelace through it and used a shoelace tie to secure the box to the camera.
Then I use my DSLR with a 13mm macro ring and a 50mm lens to actually shoot the picture.
And this is what the final product looks like: