Well, it has taken almost 70 years for tumble action washing to emerge as the most efficient way to do laundry although I am not so sure about the gentleness of the current HE tumble action washers that do seem rough on fabrics because of using so little water that fabrics rub against each other instead of plunging into deeper pools of water like in older front loaders. Well plunging over a water fall and hitting rocks in the stream could be rough, too, I guess. Westinghouse used similar imagery of laundry tumbling several miles down a stream back in the days of their tilted tub with the three vanes although I don't know how many housewives were comfortable with the image of setting their laundry loose to be washed down a stream.