There were many different ideas about purity in antiquity. A particularly strict view was adopted by the Pythagoreans, who applied the restrictions placed on people who wished to take part in sacrifices to the whole of their lives, and also observed particular taboos not kept by others. This text shows one version of the Pythagorean regime of purity.
2 From Alexander Polyhistor, Pythagoric Memoirs
Purity (hagneia) is through purifications (katharmoi), baths (loutra) and besprinklings (perirrhantēria); by keeping pure of deaths and births and all pollution; by abstaining of carcasses and flesh as foods, of the fish mullet and black-tail, of eggs and animals born from eggs, of beans and everything else that those who perform the mysteries (teletai) in temples (hiera).