In Christianity the cross is everywhere, no matter whether in the Russian form or Latin form or other forms. It seems very odd, then, that in the archeological evidence it is virtually absent from early Christian art until about the 4th and 5th centuries. Many opine that even though the cross — because of the Crucifixion — was a central part of Christian teaching, Christians were not in favor of advertising it visually because it was an instrument of shame and execution to ordinary Romans, a sign of criminals. In fact one of the earliest depictions considered to be of the Crucifixion is a wall graffito apparently making fun of a Christian named Alexamenos, showing him worshiping a God who is crucified. The graffito, found near the Palatine hill in Rome, gives Jesus the head of an ass. It may date to the beginning of the 3rd century.
There has been some talk that the earliest Christian representation of the Crucifixion is not found in graffiti or carvings or paintings, but rather in early Christian papyrus manuscripts of the Gospels. Why do some think that?
It is because of an abbreviation for the word cross (Greek stauros) found in some such early papyri. Instead of writing the word out as CΤΑΥΡΟC, they instead abbreviate it as CTPON, but combine the letters T (tau) and P (rho). so that the circle of the rho is placed atop the tau.
There is speculation that this may have been done to represent the body of Jesus on the cross, the circle of the rho forming his head. You can see what it looks like in this photo of Bodmer Papyrus 75, in the line giving “Luke” 14:27, where “cross” is found in the grammatical form CTAΥΡΟΗ/STAURON
ὅστις οὐ βαστάζει τὸν σταυρὸν αὐτοῦ καὶ ἔρχεται ὀπίσω μου, οὐ δύναται εἶναί μου μαθητής.
Hostis ou bastazei ton stauron autou kai erkhetai opiso mou, ou dunatai einai mou mathetes.
“Whoever does not carry his cross, and come after me, cannot be my disciple.”
These early papyri, however, were discovered in Egypt, which has soil dry enough to preserve ancient papyrus documents. That gives a possible alternate reason for the “crucified man” appearance of the so-called Staurogram abbreviation.
The monuments of ancient Egypt — which have lasted even to our own time — are filled with hieroglyphic symbols, and one of the most prominent of these is the ankh. “Ankh” in ancient Egyptian signified “to live” — life.
It is found in the common ancient Egyptian phrase Ankh em Pet — “Live in Heaven,” i.e. “Live forever.”
In the image below, for example, we see the Goddess Isis giving life to the nostrils of Queen Nefertari — one of the wives of Pharaoh Rameses the Great — through the symbol of the ankh:

The ankh — the “cross before the cross” — would have been a familiar symbol to early Egyptian Christians, who may have simply transferred the “life-giving” notion of the ankh from the ancient Egyptian religion to the written Gospel manuscript abbreviation for the cross. Whether the staurogram also was a kind of “stick figure” image of the crucified Jesus is open to question, but in the absence of clear evidence we are free to keep an open mind.
It is possible also that the papyri with the staurogram are not as early as previously thought. There is some speculation that instead of dating from 175-225 c.e., Papyrus 75 may be as late as the 4th century, because of its similarity of text to Codex Vaticanus, which would put the presence of the Staurogram in the same period as the known appearance of the cross in Christian art — but that too is speculation.