Historical Rules · 29 September 2017
Rule 712.3b
Official source text from the 29 September 2017 Rules release
While the two cards of a meld pair are on the battlefield as a melded permanent, the object represented by those cards has only the characteristics of the combined back face, and its converted mana cost is the sum of the converted mana costs of its front faces. If a permanent is copying a melded permanent, the converted mana cost of the copy is 0. See rule 202.3c.