This is my first attempt at a quadruple exposure in-camera using the Canon 6d's multiple exposure mode. The first shot was a shadow of a man on the streets of Manhattan. For the second frame I wanted to add more texture and photographed the white drop ceiling of an office building. The third frame was a close-up of a metal A/C vent which is slightly visible in the upper right hand corner. The fourth and final frame included the leaves of a plant which I tried to place in a way that would frame the original shadowy subject. I got lucky with the placement.
This was done with the "additive" method of multiple exposure. Essentially, you under expose each frame as they are all part of the collective exposure. Here's a look at how the menu looks to set up your preferences.
The shot was then opened in the iPad with the 6D's wifi feature and converted to B&W in the very powerful Photoshop Touch app which sells for $10.