The mechanical clock was self-contained, and once horologists learned to drive it by means of a coiled spring rather than a falling weight, it could be miniaturized so as to be portable, whether in the household or on the person. It was this possibility of widespread private use that laid the basis for 'time discipline,' as against 'time obedience.' One can ... use public clocks to simon people for one purpose or another; but that is not punctuality. Punctuality comes from within, not from without. It is the mechanical clock that made possible, for better or worse, a civilization attentive to the passage of time, hence to productivity and performance.