Zoroastrian ritual exposure of the dead is first known of from the writings of the mid-5th century BCE Herodotus, who observed the custom amongst Iranian expatriates in Asia Minor. In Herodotus' account (Histories i.140), the rites are said to have been "secret", but were first performed after the body had been dragged around by a bird or dog. The corpse was then embalmed with wax and laid in a trench.:204
While the discovery of ossuaries in both eastern and western Iran dating to the 5th and 4th centuries BCE indicates that bones were isolated, that this separation occurred through ritual exposure cannot be assumed: burial mounds, where the bodies were wrapped in wax, have also been discovered. The tombs of the Achaemenid emperors at Naqsh-e Rustam and Pasargadae likewise suggest non-exposure, at least until the bones could be collected. According to legend (incorporated by Ferdowsi into his Shahnameh), Zoroaster is himself interred in a tomb at Balkh (in present-day Afghanistan).
Writing on the culture of the Persians, Herodotus reports on the Persian burial customs performed by the Magi, which are kept secret. However, he writes that he knows they expose the body of male dead to dogs and birds of prey, then they cover the corpse in wax, and then it is buried. The Achaemenid custom is recorded for the dead in the regions of Bactria, Sogdia, and Hyrcania, but not in Western Iran.
The Byzantine historian Agathias has described the burial of the Sasanian general Mihr-Mihroe: "the attendants of Mermeroes took up his body and removed it to a place outside the city and laid it there as it was, alone and uncovered according to their traditional custom, as refuse for dogs and horrible carrion".
Towers are a much later invention and are first documented in the early 9th century CE.:156–162 The ritual customs surrounding that practice appear to date to the Sassanid era (3rd – 7th century CE). They are known in detail from the supplement to the Shayest ne Shayest, the two Rivayat collections, and the two Saddars
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