The Boiardo Trionfi poem is the oldest, for which we have a clear "22" as number of the trumps (rather different to the usual trumps). There are good reasons to date this poem to January 1487, wenn Lucretia d'Este, illegitimate daughter of Ercole d'Este married ... the highest trump in the Boiardo poem addressed the Roman Lucrezia.
Have you got a link to the full argument for 1487, I remember reading some fuller explanation somewhere sometime, but having searched can't find it. I do remember I found the argument rather weak, but perhaps the argument has been more fully expanded since then.
The arguments for an earlier dating is the poem itself - for a start it is not very good, far from the qualities for which the poems of his maturity are more famous. It is full of the faults of beginners (archaic language, simplistic rhymes, commonplace phrases & themes), and also its imitation of Petrarch is typical of the poetry of his youth - c.1460's.
As well as somewhat archaic Petrarch like language, there is the triumphal model, the Petrarchian women (a Petarchian woman is one that is unattainable, or a model of virtue), the four passions of the soul,* and the mention of the Petrarchian woman herself (Laura), amongst an otherwise array of women from the bible or classic history and myth.
S. Augustine. Do you know what stands in the way of your purpose of heart ?
Petrarch. That is what I want to know; what for so long I have earnestly desired to under- stand.
S. Augustine. Then listen. It was from Heaven your soul came forth: never will I assert a lower origin than that. But in its contact with the flesh, wherein it is imprisoned, it has lost much of its first splendor. Have no doubt of this in your mind. And not only is it so, but by reason of the length of time it has in a manner fallen asleep; and, if one may so express it, forgotten its own beginning and its heavenly Creator.
And these passions that are born in the soul through its connection with the body, and that forgetfulness of its nobler nature, seem to me to have been touched by Virgil with pen almost inspired when he writes--
"The soul of men still shine with heavenly fire,
That tells from whence they come, save that the flesh
And limbs of earth breed dullness, hence spring fears,
Desire, and grief and pleasures of the world,
And so, in darkness imprisoned, no more
Look upward to heaven's face."
Do you not in the poet's words discern that monster with four heads so deadly to the nature of man?
Petrarch. I discern very clearly the fourfold passion of our nature, which, first of all, we divide in two as it has respect to past and future, and then subdivide again in respect of good and evil so, by these four winds distraught, the rest and quietness of man's soul is perished and gone.
PETRARCH'S SECRET Trans. William H. Draper
Petrarch also discusses the four passions in his Remedies, for Fortunes Fair and Foul
Petrarch's Remedies address the life of man on this earth. Of all living creatures, man alone is endowed with the powers of reason—memory, intellect, and foresight—hence capable of thinking in terms of the past, the present, and the future. This unique gift allows man to consider, to weigh, and to judge before be wills and acts; yet he remains subject to his natural emotions and impulses which, more often than not, deceive the mind and interfere with its findings. Man has to negotiate the inner conflicts between reason and the senses as he tries to cope with the conflicts of this world, the exigencies of life?
This action is represented as man's everlasting war with Fortune, the ancient goddess Fortuna, fickle and inexorable, who smiles and frowns on all men, granting prosperity today, inflicting abject adversity tomorrow—the hidden cause behind the ups and downs of man." The battle involves each man's reactions to the "two Fortunes," fair and foul, as they beset him. Victory or defeat is implicit in his state of mind at the end of each encounter, which, in turn, decides how he will fare during the next one. Fortune herself is beyond these earthly circumstances. Whether she reigns supreme as willed by God, or is invoked as a popular figure responsible for the inexplicable, she remains forever man's existential dilemma.
The allegorical battle in every man's bosom, which takes place in the concrete, particular world familiar to the contemporary upper-class reader or listener : against a background of universal instability and cosmic strife, is fought by Reason in debate with the four Passions borne by Fortune's emissaries, Prosperity and Adversity, two sisters who, at the same time, each gave birth to twins: GaudiumJoy—and Spes sive Cupiditas—Hope or Desire—the children of Prosperity; and Dolor—Sorrow—and Metus—Fear—the children of Adversity.' Joy and Sorrow are concerned with the past and the present; Hope or Desire and Fear, with the future." The Passions afflict the mind, as diseases the body.
In the ensuing psychomachia—battle of the mind—the weapons of the attacking four Passions are their very essence--man's natural proneness to joy and wishful anticipation, to sorrow and to fear. Reason's weapon against their onslaught is virtue and its corollaries, man's power to think, will, and act right toward God and fellow man." Specifically, Reason urges the exercise of moderation and patience, and all their manifestations, as active ingredients of remedies for the ills caused by Prosperity and Adversity, respectively, and rings the changes on an involved system of the virtues, confusing to modern readers, but probably much less so to those of Petrarch's time."
"Petrarch's Remedies, for Fortunes Fair and Foul" p.xxiii, Trans. Conrad H. Rawski