Histories
Herodotus
Herodotus. Godley, Alfred Denis, translator. Cambridge, MA; London: Harvard University Press; William Heinemann, Ltd., 1920-1925 (printing).
While they were making these plans, by coincidence the following happened. The Magi had resolved after consideration to make a friend of Prexaspes, because he had been wronged by Cambyses (who had killed his son with an arrow) and because he alone knew of the death of Cyrus' son Smerdis, having himself been the slayer; but besides this, because he was in great repute among the Persians.
For these reasons they summoned him and tried to make him a friend, having bound him by tokens of good faith and oaths to keep to himself and betray to no one their deception of the Persians, and promising to give him all things in great abundance.
When Prexaspes agreed to do this, since the Magi importuned him, the Magi made this second proposal to him, that they should call an assembly of all the Persians before the palace wall, and he should go up on to a tower and declare that it was Smerdis son of Cyrus and no other who was king of Iran [53,32] (nation), AsiaPersia.
They gave him this charge, because they thought him to be the man most trusted by the Persians, and because he had often asserted that Cyrus' son Smerdis was alive, and had denied the murder.
When Prexaspes said that he was ready to do this too, the Magi summoned the Persians together, and brought him up on to a tower and bade him speak. Then, deliberately forgetting all the Magi's instructions, he traced the lineage of Cyrus from Achaemenes downwards; when he came at last to the name of Cyrus, he recounted all the good which that king had done to Iran [53,32] (nation), AsiaPersia,