Legendary ancient inscription, variously said to have been written by the Gods Thoth, Hermes, or Hermes Trismegistus, and considered to form the basis of knowledge for the fields of alchemy and the more theurgical aspects of Hermeticism. Source of the common aphorism, “As above, so below”.
This phrase in its entirety reads, in Latin: Quod est Inferius est sicut quod est Superius, et quod est Superius est sicut quod est Inferius, ad perpetranda Miracula Rei Unius. In English: “That which is below is like to that which is above, and that which is above is like to that which is below, to complete the miracle of the One Thing.”
A good introductory analysis of the Emerald Tablet and its contents can be found at altreligion.about.com. Various other examples and translations of the tablet may be found online, including: