Historical Rules · 17 July 2015
Rule 103.6
Official source text from the 17 July 2015 Rules release
In a Planechase game, the starting player moves the top card of his or her planar deck off that planar deck and turns it face up. If it’s a plane card, that card is the starting plane. If it’s a phenomenon card, the player puts that card on the bottom of his or her planar deck and repeats this process until a plane card is turned face up. (See rule 901, “Planechase.”)