The Nautilus Upright Squat Machine
During the "Colorado Experiment" Casey Viator famously gained 63 pounds of muscle mass in 28 days. The workouts were brief and intense and while not an "experiment" in a truest sense of the word, it did show that dramatic results were quite possible under a certain set of circumstances. Interestingly, much of the equipment used was in fact, experimental, and never actually made commercially available.
The Nautilus Upright Squat Machine, shown here, is a good example of this. This machine was designed to provide all the benefits of the barbell squat, while reducing or eliminating the drawbacks. This was the only leg machine that Casey used in every workout for the duration of the Colorado Experiment. While it was effective, the potential for the user to be catapulted right out of it was deemed far too great, so this was the only one ever manufactured.