If you have a gameshark or an action replay and you select the levitation code for OoT, use that ability to enter the Geredo Fortress as a child. Go up to treasure chest on top of the fortress where theres usualy a heart piece. Instead there will be a magic mushroom just like the one you get from the old bum in the Lost Woods as an adult. Even weirder is that you can do the Biggoron Sword Quest twice by getting this second secret shoom here. Its really strange that it exists in that chest in the past but not in the future, however the heart piece is located sitting in the lookout balcony above the prison cell in the past. This is really strange...