Where did Cdl. Cajetan write that a Dominican commits a mortal sin if he studies <4 hours a day?

Joret, O.P., *Dominican Life* pp. 300 -1 claims: > The great theologian [\[Cdl. Tommaso de Vio Gaetani\] Cajetan][3] , who became Master General of our [Dominican] Order, went so far as to assert that a Friar Preacher who did not study for four hours a day could scarcely be held to escape the guilt of mortal sin. Where did Cdl. Cajetan write this? Quétif & Échard, *Scriptores Ordinis Praedicatorum* (vol. 2) p. 16 : > *Unde fertur dicere solitum, sodalem Prædicatorum vix se a peccato mortali excusare, qui quoto die quatuor horas studio non impenderit.* > >Hence the usual, a member of the Preaching [order] barely excuses himself from mortal sin who each day does not spend four hours studying. But they do not say where he wrote this.