smithsonianlibraries
smithsonianlibraries:

detail from Hoover : the story of a crusade. (1926)

The marks on the carpet show how long each stroke should be and a metronome guides her in making a given number of strokes per minute. By measuring her carbon—dioxide exhalation while she works, the amount of energy required to sweep with different devices and in different ways—slow, fast, long strokes, short strokes, etc.—is accurately determined. Such tests were made to determine Hoover technique and they demonstrated that the Hoover offersthe least fatiguing way of cleaning carpets and rugs

smithsonianlibraries:

detail from Hoover : the story of a crusade. (1926)

The marks on the carpet show how long each stroke should be and a metronome guides her in making a given number of strokes per minute. By measuring her carbon—dioxide exhalation while she works, the amount of energy required to sweep with different devices and in different ways—slow, fast, long strokes, short strokes, etc.—is accurately determined. Such tests were made to determine Hoover technique and they demonstrated that the Hoover offers
the least fatiguing way of cleaning carpets and rugs