Nechepso and Petosiris were a pair of legendary figures whose names were attached to a highly influential set of astrological texts in antiquity. Together they were the most widely quoted and influential authors during the Hellenistic tradition of astrology, which lasted from approximately the 1st century BCE until around the 7th century CE.

The two were often treated as a pair, although sometimes one was cited independently from the other, which makes the relationship between their works somewhat uncertain.

The texts attributed to them are generally thought to have been composed sometime around the late 2nd century or early 1st century BCE, with the earliest references to them appearing in the early 1st century CE.

Despite the fact that they were the most influential astrological authors in antiquity, none of the works attributed to Nechepso and Petosiris survived into the present day. All we have of their works is a collection of fragments, quotations, and citations by later authors who drew on their texts and sometimes mentioned doctrines contained in them.

Names and Epithets

Nechepso is frequently referred to as “the king” (ὁ βασιλεύς), especially by Vettius Valens, who also sometimes calls him “the compiler” (ὁ συγγραφεύς).

Together Nechepso and Petosiris are sometimes referred to as “the Egyptians” or “the ancients” (οἱ παλαιοί).

Ptolemy once seems to refer to Petosiris as “the ancient one” (τὸν ἀρχαῖον) during a discussion of the length of life technique (Ptolemy, Tetrabiblos, 3, 11: 1), although this is an inference based on other authors who associate Petosiris with the technique that was used to measure the length of a native’s life.

Dating of Nechepso and Petosiris

The earliest reliable reference to Nechepso and Petosiris by an astrologer is from Thrasyllus, who died in the year 36 CE. Only a summary of Thrasyllus astrological text survives, but would have been written sometime around the early 1st century CE. This would place the Nechepso-Petosiris text(s) as having been composed sometime in the 1st century BCE at the latest, although some scholars have speculated that it could have been written as early as the late 2nd century BCE.

Titles of Their Works

The title of Petosiris’ work was Astrological Matters (Ἀστρολογούμενα) according to the Suda, a 10th century Byzantine Greek dictionary and encyclopedia.

Valens mentions a work by Petosiris that he calls the Horoi (Ὅροι), which could mean either Boundaries or Definitions (Valens, Anthology, 2, 3: 3). The title Boundaries might connect it with the astrological concept known as the “bounds” or “terms” (horia). On the other hand, it would not be surprising for one of the purported founders of Hellenistic astrology to have written a work defining basic terms and concepts. The only thing that Valens tells us about the text in this particular chapter is that Petosiris dealt with the Lot of Fortune in a way that was similar to Nechepso.

Critical Editions

The standard collection of fragments by Nechepso and Petosiris was published by Ernst Riess in the 1890s:

  • Ernestus Riess, “Nechepsonis et Petosiridis fragmenta magica,” in Philologus, supplement 6, 1891-93, pp. 325-394.

This edition is available online in two places. The first is a PDF of an old photocopy made by Chris Brennan, and the second is a direct link to a higher quality scan made available more recently from Google Books:

This was based on his dissertation, which is essentially the same but with a little more introductory content, published in 1890:

  • Ernestus Riess, Nechepsonis et Petosiridis fragmenta magica, diss., Bonn, 1890.

The dissertation is available online through Google Books:

Stephan Heilen published a more up-to-date list of fragments and testimonia as part of an important article on Nechepso and Petosiris that was published in 2011:

  • Stephan Heilen, “Some metrical fragments from Nechepsos and Petosiris,” in La poésie astrologique dans l’Antiquité. Textes réunis par Isabelle Boehm et Wolfgang Hübner. Actes du colloque organisé les 7 et 8 décembre 2007 par J.-H. Abry avec la collaboration d’I. Boehm, Paris, 2011 (Collection du Centre d’Études et de Recherches sur l’Occident Romain CEROR. 38), pp. 23-93.

Note that while Heilen’s article contains some of the metrical fragments attributed to Nechepso and Petosiris, it is not a collection of all of the fragments themselves, but just a list of where to find them.

Bibliography

Fuentes González, P.P., “Néchepso-Pétosiris”. In: R. Goulet (ed.), Dictionnaire des Philosophes Antiques, Vol. IV: De Labeo à Ovidius. Paris: CNRS, 2005, pp. 601-615. [Link]

Heilen, Stephan, “Some metrical fragments from Nechepsos and Petosiris,” in La poésie astrologique dans l’Antiquité. Textes réunis par Isabelle Boehm et Wolfgang Hübner. Actes du colloque organisé les 7 et 8 décembre 2007 par J.-H. Abry avec la collaboration d’I. Boehm, Paris 2011 (Collection du Centre d’Études et de Recherches sur l’Occident Romain CEROR. 38), pp. 23-93.

Pingree, David, “Petosiris, Pseudo-,” Dictionary of Scientific Biography, vol. 10, ed. Charles C. Gillispie, Charles Scribner’s Sons, New York, NY, 1974, pp. 547-549.

Ptolemy, Claudius, “Tetrabiblos,” ed. Wolfgang Hübner, Claudius Ptolemaeus, Opera quae exstant omnia, vol 3, 1: ΑΠΟΤΕΛΕΣΜΑΤΙΚΑ, Teubner, Stuttgart & Leipzig, 1998.

Riess, Ernestus, Nechepsonis et Petosiridis fragmenta magica, diss., Bonn, 1890.

Riess, Ernestus (ed.), “Nechepsonis et Petosiridis fragmenta magica,” Philologus, supplement 6, 1891-93, pp. 325-394. [PDF] [Google Books]

Rochberg, Francesca, “Petosiris,” in The Encyclopedia of Ancient Natural Scientists,  ed. Paul T. Keyser, Georgia L. Irby-Massie, Routledge, Abingdon, Oxon/New York, NY, 2008, pp. 637-8.

Suidae Lexicon, ed. Ada Adler, Verlag Teubner, Stuttgart, 5 vol., 1928-1938.

Valens, Vettius, “Anthology,” edited in Vettii Valentis Anthologiarum Libri Novem, ed. David Pingree, Teubner, Leipzig, 1986.

Article Information

  • Author: Chris Brennan
  • Originally published: January 21, 2012 |   Last updated: February 5, 2016
  • Article notes:  This article is currently incomplete, and I need to add in some citations and additional reference texts.
  • Cite this article: Chris Brennan, “Nechepso and Petosiris,” The Hellenistic Astrology Website, February 5, 2016, https://www.hellenisticastrology.com/astrologers/nechepso-and-petosiris/