In 1667, we recall, Milton received an initial £ 5 for Paradise Lost with a promise of £ 5 more if the edition sold out and further payment of £ 5 each for second and third editions. Twenty-seven years later, Dryden's far more sophisticated contract with Jacob Tonson for his translation of Virgil specified that the author was to be paid £ 200 in four £ 50 installments while the work was underway, and it spelled out complex arrangements for two different types of subscription copies.

Rose, Mark. Authors and Owners: The Invention of Copyright.
Cambridge: Harvard University Press, 1993. 37.