I had never seen a baby barrel cactus before and really didn't think I would be able to find one either, but I did. You can see by the size of the rock pebbles this little feller isn't very big at all. What is impressive is how much effort is expended to get those spines up and out there in size before the plant really begins to grow. A real good defense mechanism.
Some close-ups of the spines on a mature barrel cactus.