" White bought a pound of dry rushes for one shilling and counted 1,600 stems. Enough grease to prepare them—six pounds—cost two shillings more. White timed one of these rushlights: it burned for fifty-seven minutes. If his sixteen hundred rushes averaged only a half hour each, he calculated, “then a poor man will purchase eight hundred hours of light, a time exceeding thirty-three entire days, for three shillings. . . . An experienced old housekeeper assures me that one pound and a half of rushes completely supplies his family the year round, "

― Richard Rhodes , Energy: A Human History