There’s a lot of miracles associated with the various relics of the True Cross, and obviously nobody can know them all. In Venice, however, there are a lot of famous paintings referring to particular miracles that happened around there, so it’s helpful to know the story!
Here’s a journal article I came across which seems to address the problem, and describes some Italian books about it, including one very early, forgotten one which seems to have been influential:
An Incunabulum of the Miracles of the True Cross of the Scuola Grande di San Giovanni Evangelista, by Patricia Fortini Brown.
The article also notes that Bellini’s “Procession in the Piazza San Marco” is yet another miracle story!!! I didn’t know that!!
The painting shows the procession, big just like in real life, with the True Cross under a canopy in the fashion of a Eucharistic procession. Meanwhile, between the procession members and almost at the feet of a candlebearer, we see that one red-robed merchant kneels at the side of the procession. He is praying for the health of his son, and he will return home to find the boy completely healed, from the moment of his prayer. So it’s life in the big city, where we don’t always see grace happening or understand the most important moments. It also allows all the confraternity members to get their picture taken, because the faces of procession and crowdmembers are Venetians who helped fund these kinds of paintings.
Apparently this offends a lot of art critics. Eh, I think they are over-nice in their tastes. Everybody likes to have their picture taken, and it is doctrine that there is always a “cloud of witnesses” around every event, much less historical events. Donors always got their picture taken in the Middle Ages, and it seems to have helped the piety of donors to be able to picture themselves “being there.” It may have annoyed some of their neighbors, possibly; but even today, most people like to see their neighbors or friends or family in a realistic mural. I suspect that this sort of painting was an outgrowth of the pious idea of meditating by picturing oneself as present at various Biblical events; and some people seem to like picturing themselves with their friends and family in such meditations.
Here’s another very cool miracle painting: “Miracle at the Bridge of San Lorenzo.” The confraternity of San Giovanni Evangelista has just received a relic of the True Cross, and has been processing it all around the city. The bearer of the relic was jostled while crossing a bridge to go to the Church of San Lorenzo on St. Lawrence’s Day. He dropped the piece of the True Cross over the bridge and toward the canal — but it hovered safely above the canal water for several minutes, only descending when the confraternity’s head jumps into the canal to go get it. (It had evaded previous attempts by folks in boats or by swimmers, by just remaining serenely out of reach. You can see the poor lay confraternity members swimming around in their procession outfits, some normal people in their medieval skivvies, and at least one guy with his robe half off.)
Nothing else weird happened until they tried to take the True Cross piece to the funeral of a confraternity member at the Church of San Lio. The member had refused to participate in any of the processions or go to anybody else’s funeral, including those of confraternity brothers; and he secretly had lived a bad life, visiting brothels and taverns often and apparently dying unrepentant. People in the lay confraternity were vowed to live a pious and decent life, and to help out with the processions and funerals, so he also died breaking his promise. So the piece of the Cross refused to enter the church and be perceived as honoring this guy. The painting, “Miracle in the Campo San Lio,” shows the neighbors all watching this embarrassing scene from their windows. Eventually they just used a regular cross from the church for the funeral.