Cardini identifies the "bouquet of three ostrich feathers" as attached to Piero's horse. Then he says of Cosimo's horse that it, too, has Piero's emblems on it:
Cosimo's horse also bears, on the vermilion breastplate, a frieze consisting of a chain of intertwined diamond rings - a motif found in several places in the chapel; in the center of each ring in the chain, a capital Latin letter forms the word "Semper," Piero's motto. The sides of the breastplate, also vermilion, are decorated with golden peacock feathers: the peacock, in turn, has been interpreted as one of Piero's emblems ...
If it's Cosimo's horse, it ought to be Cosimo's emblem, not Piero's. But I don't know what he is talking about: it is Piero's white horse that has the peacock feathers. Perhaps he meant to say "Piero's horse also bears . . . " Cosimo seems to be the old man riding the mule (long ears). The same white horse has the rings alternating with the "bouquet of ostrich feathers" on the bridle and the peacock feathers on the part below the bridle.
And where is Giovanni? From the devices, it should be him behind Piero on the same horse, the man usually identified as Carlo. It seems strange that the illegitimate son should be included and not Giovanni. He didn't die until 1463, the latest year for the completion of the fresco.
The Motto "Semper" does not help. It is true that "Semper" was Piero's motto; but it also appears as part of the peacock emblem in mss. commissioned by Giovanni. Francis Ames-Lewis in "Early Medicean Devices," 1979, in JSTOR, pp. 131-2 (I omit the footnotes):
Ten books are inscribed as having been commissioned by Giovanni (44); of these the Cicero, Philippicae has in the decoration the Medici stemma enclosed within what appears to be a diamond ring, and the Silius Italicus has four times repeated a diamond ring entwined within which is the word SEMPER (P1. 37e). Clearly Giovanni was at liberty to use variants of the family device of the diamond ring generally associated with Piero di Cosimo.
If both brothers used SEMPER, they may simply be inheriting something from Cosimo. Cosimo is sometimes suggested as having been the first to commission works in the "tondo" form, used in a couple of his "Adoration of the Magi" paintings. The circle, besides being the shape of the Cosmos, is a symbol of never-ending time, eternity in that sense (not Petrarch's end of time). Ames-Lewis cautiously does not draw any conclusions about Cosimo. Hibbert may have been less cautious; but Ames-Lewis does not mention the peacock feathers sprouting from the Medici stemma above the iron lantern on the Palazzo Medici.
Ames-Lewis goes on to describe four manuscripts done for Giovanni that "have in their direction a very prominently placed peacock" (p. 132) several more have peacocks that seem to be a device rather than merely decoration. In Augustine's
De Civitate Dei a peacock stands frontally above the Medici stemma with the words "REGARDE MOI" behind it on a scroll. They appear together with the stemma also in a Cassian,
Vita Patrum. He mentions two other mss., adding in a footnote that in mid-century Italian mss. peacocks are not common, the exceptions being for Alfonso of Aragon and one that seems purely decorative done for Piero. About "Regarde moi," while not dismissing reference to Augustine's idea of its incorruptible flesh (after all, one of the examples is in Giovanni's copy of a work by Augustine), he says:
it is more probably derived from classical sources; he may for example be comparing his peacock with Juno's, or following Pliny's comments on the peacock's knowledge of its own magnificence: (58)
. . . omnesque reliquas in iis pavonum genus, cum forma, intelectus eius et gloria. Gemmantes laudatus expandit colores, adverso maxime Sole, quia sic fulgentius radiant . . .
It may be of interest that Ames-Lewis wonders if Piero's "ostrich feathers" are such; they could be the feathers of a molting falcon, which would be consistent with Piero's choice of the falcon as his device (p. 129). The Medici's paintings with peacocks also have birds of prey swooping down on birds with more vegetarian diets. Ames-Lewis says (Ibid., n. 30) that the earliest reference to ostrich feathers in connection with the Medici that he knows about appears in 1513 (perhaps more is known since 1979, when Ames-Lewis wrote this); they were, however, associated with the Sforza of Pesaro. He also notes that the image of a molting falcon is "listed by Segni as one of Piero de' Medici's devices and recorded by Cambi on the standard for the 1459
Spettacolo" (p. 138).
Ames-Lewis also mentions in passing that before the Medici, peacocks were used in north-Italian decoration. He cites a 1434
Adoration by Stefano da Verona in the Brera (
https://it.wikipedia.org/wiki/Adorazion ... da_Verona)) And the Visconti Hours. Although Kirsch and Meiss say only that its presence there is a "reminder of the peacocks which adorned the Visconti gardens," Ames-Lewis is not so sure it was merely decorative, because (pp. 133-34, n. 55)
The motif is prominent in other Visconti MSS, such as Paris, Bibl. Nat. MS lat. 6520, Albertus Magnus, De Animalibus, fol. I., Chambery, Bibl. municipale MS 4, Breviary, fol. 43, ... and a missal for Mantua Cathedral.
He notes that (Ibid)
Filippo Maria Visconti's motto "a bon droit" is indeed echoed in the inscription DROIT which appears on the first page of Giovanni de' Medici's Augustine in which the peacock stands over the motto REGARDE MOI.
The peacock feather on the CY King of Coins in that regard would seem to identify the wearer as a Visconti, so rich that he needs no handout, unlike Francesco Sforza. This last was observed by Phaeded, a good point. So I retract my suggestion that it might have been a dig at Cosimo, regardless of whether the latter had the peacock feather as a personal device. However, it seems to me that in that case there is no derision of the peacock on that card, far from it; if there is a connection to Marziano, the moral has been reversed, and the more Peacocks one has the better, if one also is strong in Eagles.