The idea and tendency of such a scheme for the history of the world are easily understood: these periods of 3000 years, which can be increased or diminished without alteration of the sense, have only a dogmatic value. We cannot obtain from them any chronological date for the appearance of Zarathrustra, nor can we obtain such a date by the attempt to go back from the chronological statements in recent Parsee works to the older periods. We may leave unnoticed the assertion in the book of Arda Viraf that the true faith had existed in purity for 300 years down to the time that Alexander came into Iran (p. 50), which would thus bring Zarathrustra into the seventh century B.C. The Bundehesh allows 460 years for the reigns of the Sassanids, 246 for the Askanids, _i.e._ the Arsacids, 16 for Alexander, before whom come Darai the son of Darai with 14 years, Darai Chirazatan with 12, Huma (a queen) with 30, Vohumano with 112, and Vistaçpa with 90,--all subsequent to the appearance of Zarathrustra.[151] According to this, 996 years elapsed between Zarathrustra and the fall of the Sassanids, and he would thus, if we reckon from the battle of Nahavend (640 A.D.), be placed in the year 356 B.C., in the reign of Artaxerxes Ochus. But even if we alter the incorrect items in the text of the Bundehesh in accordance with our better knowledge, we do not arrive at any result which is even apparently certain. The dominion of the Sassanids, down to the date of the battle, did not last 460 but only 414 years; on the other hand, the Arsacids reigned for 476 years, not for 264.[152] The empire of Alexander, if we add the reigns of the Seleucidæ to his own, occupied 80 years instead of 14, and if in the place of the 26 years of the two Darais of the Bundehesh, who represent the kingdom of the ancient Achæmenids, we put the old Persian kingdom with 229 years, and add to these items the numbers given in the Bundehesh for Huma, Vohumano, and Vistaçpa, after the appearance of Zarathrustra, which amount to 232 years, Zarathrustra would have commenced his work 1431 years before the battle of Nahavend, _i.e._ in the year 791 B.C. But who can guarantee that Cyrus, the Persian, overthrew the empire of the Medes in the year when Huma, the supposed daughter of Vohumano, died; or that Huma reigned for 30 years? How could Vohumano, the grandson of Vistaçpa, and son of Çpentodata (p. 38), have reigned 112 years, and Vistaçpa himself 90 years after the appearance of Zarathrustra? Huma is not merely a doubtful person, she is altogether fictitious. She is said to have been the mother of Darai Chirazatan, _i.e._ Darius I., and to have been called Shamirain, _i.e._ Semiramis, but her brother was the first Sassan, the ancestor of the Sassanids. As the later Arabs and Persians, including Firdousi, are no better informed,[153] we see clearly that the remembrance of the Achæmenids had almost entirely died out at the time when these writings were composed; only the name of Darius remained, and an attempt was made to connect this name with Vistaçpa by two fictitious names, Vohumano, _i.e._ the good spirit, and Huma. Besides Vistaçpa's son Çpentodata (Isfendyar) and Hutaoça, the wife of Vistaçpa, the Avesta mentions a woman, "the pure Huma,"[154] out of whom this queen must have been formed. It is clear that the tradition of the East, like the Avesta, broke off in the generation after Vistaçpa, and that in the Arabian period only the names Darai and Iskander could be placed between Vistaçpa and the Arsacids.