Phaeded: I have no quarrel with your connecting Giangaleazzo with Mainz and the Stuttgart cards, far from it. I support it, as will become clear later in this post.
But then you say:
Have you yet to find any pre-16th century reference associating these four as a group in the manner that you have, or just these tortured interpretations of history? Failing that, did any contemporary source posit any two emperors with two popes as a group? If no, I'll stick with Charles V being crowned Holy Roman Emperor by Pope Clement VII in Bologna in 1530 as the reason the "papi" were created and indeed, why they are associated with the Bologna variation of tarot. The Papi are late and there simply is no earlier evidence.
I do not know what "tortured interpretations of history" you are referring to. That Louis IV was an excommunicated emperor, Nicholas V an antipope, John XXII a pope, and Charles IV a "true" emperor who was defeated by Louis before becoming emperor are all hard facts, as you call them. No need of anyone to make them a group: they all lived at around the same time and interacted with one another. I don't know what else is needed, other than some reason to connect this fact with the early tarot, which I did.
As for Charles V and Clement VII, the context of my post was that I was trying to make sense of the four labels "pope" "antipope" "excommunicated emperor" and "true emperor" as personages interacting with one another in a way that could result in one defeating another, as the "equal papi" rule supposes, during the time of Guelfs and Guibellines. While the "true" emperor and "true" pope did not in fact turn on each other, historically "true" popes did turn on "true" emperors and vice versa, in the period in question. I was trying to make a credible case for those particular four in relation to the "equal papi" rule. The title of my post was "The 'equal papi' rule in the context of medieval Italy". Charles V and Clement VI have nothing to do with Guelfs and Guibellines, the theory proposed by Mamellini and Buini, so they are excluded from consideration for the purposes of the post.
As far as early writings about the tarot are concerned, it is in relation to Piscina that Charles V and Clement VII are credible candidates. In fact they are one of two examples that Piscina gives, where an emperor defeated a pope, or at least his forces. He did group them together, but the fact that he did is just his theory about what the "equal papi" rule is about. That he did so doesn't make it true. (The other example was Boniface VIII, but in that case it wasn't an emperor who imprisoned the pope, but the king of France.)
I have several problems with Piscina's theory about the "equal papi" rule. One is that it doesn't justify having two of each, including an Empress and a Popess, as the deck he was using surely had. Another is that it doesn't explain why the rule would be instituted post-1530 in only two places, Piedmont and Bologna. A third is that it doesn't explain how, or why, in either place people could suddenly be induced to change the order of trumps such that four cards previously in strict hierarchy would now all be treated as equal.
I was principally addressing the "equal papi" rule. It is true that on my interpretation of Mammelini's theory, they would have all been male. That does need to be addressed. I was planning to give an argument on the other side in my next post. Well, I will do so now.
The "equal papi" rule, Part Two
There remains the problem of how to explain the "equal papi" rule in Piedmont, given that the "papi" there would have had 2 males and 2 females. Again I think we have to assume an "equal papi" rule from the beginning, someplace near or with friendly ties to Piedmont, from which Piedmont would have learned the game. A different argument would justify the "equal papi" rule in such places. There seems to have been a sense in early card games of balancing male and female: the Stuttgart hunting deck, for example, with all-male courts in two suits and all-female courts in the other. In tarocchini and minchiate there are sometimes female pages in two suits and male pages in two suits, corresponding to the two suits going from 1 to 10, as far as the power of the numeral cards, vs. the two other suits going from 10 to 1. In the Cary-Yale there are male and female pages and knights in all four suits; perhaps the females had priority in two suits and the males in the other two.
By this argument, however, only one of each would be necessary, an Emperor and Empress of equal rank, the one played last with priority. So why not just two?
Also, Kings always ranked above Queens in the same suit. It would seem that the same would be true in a trump suit.
We might say, well, there are four because there were four in the place of origin, Bologna. This begs the question. It could well have gone the other way. And anyway, we have no evidence of an "equal papi" rule anywhere before the 16th century (that Mamellini could even propose the pope-antipope-true emperor-excommunicated-one theory implies that it existed, and that there were four).
But it seems to me that there are ludic considerations that indicate four or eight rather than two or three, existing at the dawn of the game. It goes against the grain to have a suit where the cards aren't ranked. Even in Karnöffel the trumps were ranked. For such a circumstance. of two or more cards being equal, to occur, it is more likely that there were first trumps without a trump suit for them to be ranked in. That is possible only if the trumps are extensions of the suits, and the suits have no ranking among themselves. So, for example, we have an Emperor and an Empress for each suit, above the kings, with trumping power in the sense that in the right circumstances, the Emperors can prevail over any card from Empress down, and the Empresses can prevail over, say, any card Queen and below, with priority going to the Emperor or Empress played last. The Queens in this situation would be "partial trumps", as Dummett called such cards in Karnöffel.
In such a circumstance the same game could be played with only four such dignitaries, two papal and two imperial. In that case they could all be equal, or else two of each gender or type (spiritual or secular) taking priority over the other two, and among each of the two equal ones, the one last taking the trick. But still, this only works if there are at least four. To have a suit with no attached dignitaries would disturb the balance so carefully nurtured in early card games. And in fact having two with less power than the other two, i.e. with Empresses of less power than Emperors, would also disturb the balance among suits. So they have to all be equal, which is a perfectly acceptable solution, given the balance between "feminine" and "masculine" suits in various early decks.
Then when there is a trump suit, i.e. one where cards are ranked, the imperial and papal cards can be an exception, made familiar because of a previous game in which they were extensions of the suits. In that case, in the context of other cards ranked among themselves, there might even be only two or three equal papi, of both genders. Four would merely correspond best to the previous game in which they were attached to the suits. It is some small confirmation of my idea that the resulting order sometimes has males above females and sometimes spirituals above seculars, as if at one point nobody had to keep track of which it was supposed to be.
If such a rule under such conditions (equality among sexes of two types) can be granted in places we see dignitaries of both sexes, i.e. Lombardy, Ferrara, and Florence, might it not also have applied to Bologna, and the one gender version come later? That is also possible. It is only a Bolognese tradition that says otherwise. That tradition is verified only as far as the first half of the 16th century at most, as I think Mamellini's language implies. (Ross tells me that Mamellini says he found the account he reports in some "old papers". It seems to me that if he was born in 1546, "old" could go back that far, or earlier or later. As I downsize my possessions, I find old papers, and they are just papers I wrote in college. My cousin in her downsizing is finding carbon copies of letters written by her father from before she was born. They, too, are "old".)
So the theory could easily have been manufactured then, perhaps at the time the deck was reduced, and before then, the "equal papi" have been males and females. The real reason for having an all-male cast might have been to get rid of the Popess, disliked by the papal authorities, and then some proud Ghibelline family decided the game was about them. In its favor is the coincidence of the four contending dignitaries in the 12th-early 15th centuries, and especially 1324-1347, coinciding with the requirements of a game with the "equal papi" rule. But there is no evidence one way or the other, even if the coincidence with the actual facts does give us reason for taking it seriously.
Another story might have been that of Piscina, of the glorious Papacy versus the barbarian and heretic-infested Empire to the north, although in that case I still don't understand why there would need to be four males rather than two. I also cannot understand why a procession with four papal hats would indicate, or prompt, changing the four cards of the tarocchi or tarocchini in that city to four males. If the cards all had papal hats on them (or even crowns), you might have a point, but they don't. Also, it was an occasion for unity between pope and empire, not the conquest of either by the other, as the "equal papi" rule dictates.
In regard to topical relevance, another story, or theory, might be that of the two empires, eastern and western, each with their dignitaries, which met as equals in 1438-1439. But this, too, is not the right kind of situation, not contention among equals but cooperation and unity-seeking, a situation that does not occur in the game. However since that situation also did not occur in reality, the western side taking advantage of the eastern side's weakness (by insisting on on the supremacy of the western pope), resulting in the eventual collapse of that unity effort and the impending destruction of the east (by a third empire not accounted for in the game, unless by the Devil), there remains some analogy, more after 1440 than before (since Italians by and large didn't realize that the terms of unity were unacceptable to the east until later). That analogy may well have increased the popularity of the game, but it is so weak I cannot see it causing the rule.