Historical Rules · 4 October 2019
Rule 712.4
Official source text from the 4 October 2019 Rules release
If a melded permanent leaves the battlefield, one permanent leaves the battlefield and two cards are put into the appropriate zone. Example: Chittering Host, a melded permanent, dies. An ability that triggers “whenever a creature dies” triggers once. An ability that triggers “whenever a card is put into a graveyard from anywhere” triggers twice.