Herodotus 3.38

    Thus it appears certain to me, by a great variety of proofs,
that Cambyses was raving mad; he would not else have set himself to
make a mock of holy rites and long-established usages. For if one were
to offer men to choose out of all the customs in the world such as
seemed to them the best, they would examine the whole number, and
end by preferring their own; so convinced are they that their own
usages far surpass those of all others. Unless, therefore, a man was
mad, it is not likely that he would make sport of such matters. That
people have this feeling about their laws may be seen by very many
proofs: among others, by the following. Darius, after he had got the
kingdom, called into his presence certain Greeks who were at hand, and
asked- "What he should pay them to eat the bodies of their fathers
when they died?" To which they answered, that there was no sum that
would tempt them to do such a thing. He then sent for certain Indians,
of the race called Callatians, men who eat their fathers, and asked
them, while the Greeks stood by, and knew by the help of an
interpreter all that was said - "What he should give them to burn
the bodies of their fathers at their decease?" The Indians exclaimed
aloud, and bade him forbear such language. Such is men's wont
herein; and Pindar was right, in my judgment, when he said, "Law is
the king o'er all."