One of my first lessons in precision occurred at the home of my best friend when we were children. We decided it might be fun to rig a zip line across his back yard, stringing some plastic coated rope between two trees about 25 feet apart.

When it came time to experiment to see whether or not the line would hold our weight, we chose my younger brother for the test because he weighed less than the rest of us. We figured if the line would hold him, we could try the next lightest person until we all made it across the divide. My brother balked at taking the maiden run, because the line was about 10 feet off the ground, and there was no padding to cushion his fall if the rope were to break.

To ease his fears, my friend ran into his house and emerged with a throw pillow from his couch, about a foot square, and placed it about mid way between the start point and the finish of the run. Assured by this safety precaution, my little brother grabbed the slide bar and launched. The rope broke under his weight, and he plummeted to the ground, landing precisely on the throw pillow in a seated position. Unfortunately, the pillow did not provide enough cushion for the drop to avoid a solid thump, but we were pleased with our precision in placing the pillow in the right location. After that, we did not have enough rope to try again, so we abandoned our project, satisfied that we had at least learned something about geometry.