"Get a Sphaerical Cylinder, or Convex diffection of a Pyramidal Concave. Let it be that which may descend upon his right angle by half cylinder and a square, and is parted by an oblique angle."
"Of two parts it must be received pendulous, and beneath in the half of its diameter it is conveyed from the middle."
All right! Now make sure the room is dark safe for your image, which — if it is reflected rightly, Giambattista della Porta assures us in a late English translation of his astonishingly brilliant Magiae naturals — will appear to "hang in the air".
Compared to that, Mac OS X Mail's slideshow is rather mundane (if perhaps more readily available) an affair. Make sure your room is lit well, and, reflected justly, your image will appear to hang somewhere behind the monitor — and slideshow:
›› Want to see attached photos or documents up big and with exclusive focus? Here's a fast way to open attachments as full-screen slideshows right from Mac OS X Mail.