It is said that as many days as there are in the whole journey, so many are the men and horses that stand along the road, each horse and man at the interval of a days journey; and these are stayed neither by snow nor rain nor heat nor darkness from accomplishing their appointed course with all speed.
In view of all this, I have no doubt that Cambyses was completely out of his mind; it is the only possible explanation of his assault upon, and mockery of, everything which ancient law and custom have made sacred in Egypt. If anyone, no matter who, were given the opportunity of choosing from amongst all the nations in the world the set of beliefs which he thought best, he would inevitably, after careful consideration of their relative merits, choose that of his own country. Everyone without exception believes his own native customs, and the religion he was brought up in, to be the best; and that being so, it is unlikely that anyone but a madman would mock at such things. There is abundant evidence that this is the universal feeling about the ancient customs of one's country. One might recall, in particular, an anecdote of Darius. When he was king of Persia, he summoned the Greeks who happened to be present in his court, and asked them what they would take to eat the dead bodies of their fathers. They replied that they would not do it for any money in the world. Later, in the presence of the Greeks, and through an interpreter, so that they could understand what was said, he asked some Indians, of the tribe called the Callatiae, who do in fact eat their parents' dead bodies, what they would take to burn them. They uttered a cry of horror and forbade him to mention such a dreadful thing. One can see by this what custom can do, and Pindar, in my opinion, was right when he called it king of all.
(Herodotus is expressing his own feelings about the story of the madness of Cambyses)