From the Acts of Peter in the apocrypha, thought to be the source of the legend that Peter was martyred upside-down; he says this from his cross:
What is Christ, but the word, the sound of God? So that the word is the upright beam whereon I am crucified. And that which crosses it is the nature of man. And the nail which holds the cross-tree unto the upright in the midst thereof is the conversion and repentance of man. Now I give you thanks with that voice which is understood in silence, which is not heard openly, which proceeds not from the body, which goes not into ears of flesh, which is not heard of corruptible substance, which exists not in the world, neither is sent forth upon earth, nor written in books, which is owned by one and not by another: but with this do I give thee thanks: with the silence of a voice, wherewith the spirit that is in me loves you, speaks to you, sees thee, and beseeches you. You are the All, and the All is in you: and you Are, and there is nought else that Is, save you only.