The procedures by which decisions were reached at the Council of Trent were not established immediately. The papal legates who directed the assembly dealt with problems day by day and in agreement with the Pope, whom they consulted frequently. The secretary of the Council, Angelo Massarelli, however, took note of everything and left for posterity a detailed description of the methods followed, especially those that were ultimately "successful" given the Council's extraordinary results for the faith and customs of the Catholic Church. The analysis of the rules of the Council of Trent shows that they were modelled in many respects on previous ecumenical councils and that, thanks to Massarelli’s detailed description, they became of fundamental importance in drafting the rules of the First Vatican Council.
For more information on the lecture series see: https://events.gwdg.de/category/172/
Research Group “Normative knowledge in the praxis of the Congregation of the Council. The production of normative categories and models for the post-Tridentine world”