There was a transaction spendable only by someone who provided the double hash of the genesis block. How was that transaction created? I can't find it anywhere, but I remember reading about a transaction that was spendable only by someone who provided the double hash of the genesis block. Was it simply that the private key of an address was seeded with the genesis block hash and coins were sent to that address as an output? 

Is there a transaction type that allows you to specify that providing a pre-image of a hash is the only requirement of redeeming coins?
This transaction is described quite well on the wiki. 

https://en.bitcoin.it/wiki/Script#Transaction_puzzle