I first came across Fresnel lenses in a cute place. I bought a "Where's Wally pocket edition" book for my daughter and since the book was very small (A6), they

I first came across Fresnel lenses in a cute place. I bought a "Where's Wally pocket edition" book for my daughter and since the book was very small (A6), they included a small plastic Fresnel lens in a little pocket inside the front cover. This made it practical to find Wally. I have one in my card wallet for "emergencies" :)