"Since time immemorial people have always created images, yet one of the most complex image theories of the Christian cultural sphere has its origin in a picture that was not created by human hand, and is known as vera icon, Veronica, or the veil of St. Veronica, and in the thirteen century this relic was the main destination of pilgrimages to Rome. According to the legend, Saint Veronica gave her veil to Christ whilst he was carrying the cross to Calvary, and he wiped his face covered in sweat and dust with it and left a pictorial trace of his features as an imago expressa. Because of the stains, the veil lost its pristine whiteness, and the image was separated from the body. It was only through this gesture that the veil of Veronica became a picture. With the miraculous imprint of the face of God’s son on the veil, an authenticated true image of Christ was created - as a copy. In the image concept of the vem icon, the trace of the word incarnate becomes an image and it becomes a relic."
Ingeborg Reichle (2009). Art in the Age of Technoscience. Viena: Springer Verlag/Wien