"Is it ever possible,” they ask, “for copper to be transmuted into gold?” Say, Yes, by my Lord, it is possible. Its secret, however, lieth hidden in Our Knowledge. We will reveal it unto whom We will. Whoso doubteth Our power, let him ask the Lord his God, that He may disclose unto him the secret, and assure him of its truth. That copper can be turned into gold is in itself sufficient proof that gold can, in like manner, be transmuted into copper, if they be of them that can apprehend this truth. Every mineral can be made to acquire the density, form, and substance of each and every other mineral. The knowledge thereof is with Us in the Hidden Book.
(Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 197-198)