Six days shalt thou labor and do all thou art able, And on the seventh — holystone the decks and scrape the cable.

Richard Henry Dana, Jr. (1815-1882) American lawyer, politician, sailor, writer

Two Years Before the Mast, ch. 3 “Ships Duties — Tropics” (1840)
    (Source)

Dana refers to this rubric about the endless labor aboard a sailing ship as the "Philadelphia Catechism."