Crystal Skull, Isu Spyglass

An ability that triggers “whenever you cast a historic spell” doesn’t trigger if a historic card is put onto the battlefield without being cast.

You can look at the top card of your library whenever you want (with one restriction; see below), even if you don’t have priority. This action doesn’t use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.

If the top card of your library is a historic card with a disguise or morph ability, you can’t cast it face down from the top of your library with the permission granted by Crystal Skull because the resulting spell would not be a historic spell.