64 This way of acting bids fair to revive the exaggerated and senseless antiquarianism to which the illegal Council of Pistoia gave rise. It likewise attempts to reinstate a series of errors which were responsible for the calling of that meeting as well as for those resulting from it, with grievous harm to souls, and which the Church, the ever watchful guardian of the "deposit of faith" committed to her charge by her divine Founder, had every right and reason to condemn. For perverse designs and ventures of this sort tend to paralyze and weaken that process of sanctification by which the sacred liturgy directs the sons of adoption to their Heavenly Father of their souls' salvation.
Source: Mediator Dei (Vatican.va)