The Refutation of All Heresies
St. Hippolytus
I. ...Among logicians is Aristotle, pupil of Plato. He systematized the art of dialectics. Among the Stoic (logicians) were Chrysippus (and) Zeno. Epicurus, however, advanced an opinion almost contrary to all philosophers. Pyrrho was an Academic; this (speculator) taught the in-comprehensibility of everything. The Brahmins among the Indians, and the Druids among the Celts, and Hesiod (devoted themselves to philosophic pursuits).
II. Among his followers, however, who escaped the conflagration were Lysis and Archippus, and the servant of Pythagoras, Zaniolxis, who also is said to have taught the Celtic Druids to cultivate the philosophy of Pythagoras. And they assert that Pythagoras learned from the Egyptians his system of numbers and measures; and I being struck by the plausible, fanciful, and not easily revealed wisdom of the priests, he himself likewise, in imitation of them, enjoined silence, and made his disciples lead a solitary life in underground chapels.
XXII.--THE DRUIDS; PROGENITORS OF THEIR SYSTEM.
And the Celtic Druids investigated to the very highest point the Pythagorean philosophy, after Zamolxis, by birth a Thracian, a servant of Pythagoras, became to them the originator of this discipline. Now after the death of Pythagoras, Zamolxis, repairing thither, became to them the originator of this philosophy. The Celts esteem these as prophets and seers, on account of their foretelling to them certain (events), from calculations and numbers by the Pythagorean art; on the methods of which very art also we shall not keep silence, since also from these some have presumed to introduce heresies; but the Druids resort to magical rites likewise.
St. Hippolytus. "Philosophumena": The Refutation of All Heresies. translated by the Rev. J. H. Macmahon, M.A. Fathers of the Church.