In 1620, as the tenor of the comet debate turned nastier, the Holy Congregation of the Index raised the specter of the Edict of 1616 by announcing at last the necessary corrections that must be made to Copernicus's text, De revolutionibus, in order to have it removed from the Index of Prohibited Books. The congregation insisted on watering down some dozen statements by Copernicus affirming the Earth's motion, in order to make them sound more like hypothetical suggestions. Galileo dutifully penned the required changed into his own copy of De revolutionibus, though he took care to cross out the offending passages with very light strokes.
From Galileo's Daughter by Dava Sobel. Chapter 8, pages 91-92.