In the base game Dominion, Throne Room lets you play an action card twice. The Dominon complete reference guide on BGG singles out the Throne room on a Throne room play for some helpful notes.
When you play Throne Room on Throne Room, this will let you play two other cards (each twice).
What I'm not clear on is if you need to have both "other" cards in hand already to be able to do this, or can the first card played allow me to draw the card I use on the 2nd Throne room?
Is this acceptable?
Hand: Throne Room, Throne Room, Moat, Copper, Copper
Play: Throne Room, Throne Room, Moat (drawing 4), Play Laboratory (which I've just drawn using the Moat), etc...
Or do I have to have the action card already in hand to make use of the "third" Throne Room created by duplicating the second card played?