Jim Hamilton has an excellent review of Hurtado's Earliest Christian Artefacts. This includes a discussion of the tau-rho symbol,
- Hurtado then takes up the scribal practice of writing a rho upon a tau to create a “staurogram,” which appears to be an early abbreviation for the terms “cross” and “crucify” (stauros/stauroo). This monogram apparently gave rise to others, such as the chi-rho (Christos), the iota-chi (Iesous Christos), and the iota-eta (Iesous). Here we have a fascinating discussion of where this early pictogram appears and how it arose. Hurtado is keen to the notion that “the tau-rho device was appropriated initially because it could serve as a stylized reference to (and visual representation of) Jesus on the cross” (151). The “t” shape of the tau with the superimposed “P” shape of the rho presenting a simple picture of a man on a cross. This is powerful physical evidence against claims that “visual references to Jesus’ crucifixion do not predate the fourth century” and the idea that “there was ‘no place in the third century [or earlier] for a crucified Christ . . .’” (153). The textual evidence comes from manuscripts “at least as early as the late second century” (154).