As dj181 stated, Mentzer's version is Mentzers version, following his thread of exercise theory. Seems he uses the drop weight idea for each rep, adjusting for a max effort every rep. With very limited reps in a set. Tough CNS training also.
Been doing the Rest/Pause (could have named it Halt & Go just as well) for years, on and off. Productive method. The classic version is a pause of 10 to 12 seconds between each rep. For example, if you can do 200lbs for 5 fairly good rep's, than that would be the general gauge of the weight used for the bench press, with R/P. You keep the same 200lbs on the bar throughout the whole set. The surprise is that you may be doing 9 or10 reps with that 200 rather than the usually 5 rep's after the set is completed. The next workout, the reps may jump up to 12 or more with that same 200. Will need a good watch or stopwatch. We usually will have someone watching the clock , and either yell or clap their hands when the next rep is due (10-12 seconds). 3 sets seems to be the max on something like R/P, though some may do 5 sets....that should be the limit on this very focused way to train. And perhaps only once or twice a week.
R/P works extremely well with squats, Dl's , cleans and other big boy compound exercises.
Art Jones preferred to do one, and at the most, two sets of any exercise. His slow negative curl grip chins (believe from 20 to 30 seconds for the negative close grip chin...no positive chin was included..I might be wrong on that, it may be longer negative time), SS'ed with the BB curl (one set each), was all that would be required if a person was only using the standard workout equipment. You would be going to failure on each exercise, that was a given, with cheats included with the BB curls. If only doing one set, to extreme failure, once or at the very most twice a week, than perhaps failure may be an option for some. Personal view is the failure is never sought, or needed, in most any workouts. But there are exceptions if trying for a personal best/testing strength, etc; as PL'ers and Olympic lifters have been known to do. But again, not that often. Good Luck.