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wishing to follow the command of the Lord made unto Moses, about the 70 men to-be-gathered from amongst the elders of Israel, whom he had known to be the people’s old men, and teachers, so
that they might bear with him the burden of the people, and so that he himself would not be weighed down alone, and upon whom, having been led to the door of the Tabernacle, the Spirit rested, with the Lord speaking: about the Council of our brother preachers,
we perpetually establish, and ordain, that, into the hereafter, with anumbered all the Episcopal, sacerdotal, and diaconal Cardinals of whatsoever order, who now are, and to will be created in the future, that all together, shall, at no time ever exceed the number of 70,
and such number shall not be increased for any pretext, occasion, or cause, even most urgent. That if it will have happened, that one (or more [than one]), by us, or by the Roman pontiff existing at that time in the future, either to be chosen or to be pronounced as a cardinal,
we decree that an election, creation, and pronouncement of this type to be going to be null, bankrupt, and void, and to be thought to be, and that no right is acquired thus by the chosen one or ones, whether the title is in reality or in name [only], neither that anyone of them is to be held for a cardinal, or to be able for owing to be reputed [as a cardinal], nor that the stated election, creation, or pronouncement from the beginning to be invalid [valid?], and made beyond the number, if afterwards, with one or more cardinals dying, to the prescribed number, the same College may be returned, [and] on account of which things, retroactively to make good, but as from the beginning, thus from then onward perpetually it [the decree] to be of no assistance or importance."
From the time of this Infallible Constitution to the time of John XXIII no Pontiff exceeded the specified number of 70 Cardinals.
"Postquam Verus - The Cardinals of the Holy Roman Church" Const. of Sixtus V Dec 3rd, 1586
On The Number And Quality Of The Cardinals Of The Catholic Church: Sixtus V (Postquam Veras 1586)writelatin.org/papal/postquamveras.html