5 The first warning of the danger was given by Clement XII in the year 1738,(3) and his constitution was confirmed and renewed by Benedict XIV(4) Pius VII followed the same path;(5) and Leo XII, by his apostolic constitution, Quo Graviora ,(6) put together the acts and decrees of former Pontiffs on this subject, and ratified and confirmed them forever. In the same sense spoke Pius VIII,(7) Gregory XVI,(8) and, many times over, Pius IX.(9)
Source: Humanum Genus (Vatican.va)