Originally Posted by Takara
The squeaks come from where the leather seat is riveted to the seat frame. You can make them go away with a few sparing squirts of WD-40.
Actually, I think it squeaks up front at the adjusting bolt holder mechanism.
The front of the saddle can rotate (twist) around this hinge point, especially as the leather stretches and relieves tension.
And so it can squeak here at this point of movement - steel on steel. Oil it.
Also some seatposts can squeak. Check this before you pull the crank and bb. Etc.