Humboldt informs us, that “the most important ancient notice of the
relations between lightning and conducting metals is that of Ctesias,
in his _Indica_, cap. iv. p. 190. He possessed two iron swords,
presents from the king Artaxerxes Mnemon and from his mother Parasytis,
which, when planted in the earth, averted clouds, hail, and _strokes of
lightning_. He had himself seen the operation, for the king had twice
made the experiment before his eyes.”--_Cosmos_, vol. ii.