- Tradition
- Greek philosophical mysticism. Porphyry (c. 234–305 CE), pupil and editor of Plotinus.
- Translation
- Alice Zimmern, *Porphyry the Philosopher to His Wife Marcella* (London: George Redway, 1896). Public domain.
- License
- Public domain (pre-1929 English translation). Reproduced for educational and religious commentary.