Read "Capital, Volume One: The Process of Production of Capital" by Karl Marx online for free on Textopian. Full text with search, annotations, highlights, and AI-powered reading aids.
Section 1: The Limits of the Working day
We started with the supposition that labour-power is bought and sold at its value. Its value, like that of all other commodities, is determined by the working-time necessary to its production. If the production of the average daily means of subsistence of the labourer takes up 6 hours, he must work, on the average, 6 hours every day, to produce his daily labour-power, or to reproduce the value received as the result of its sale. The necessary part of his working day amounts to 6 hours, and is, therefore, caeteris paribus [other things being equal], a given quantity. But with this, the extent of the working day itself is not yet given.