[Jordan Baker]

Here is an up close copy of the famous looking straight down picture.

Notice the buckle for the strap is all the way over to the side. This would suggest that it has room left for another cushion. This is becuase the other one is being used as a kneeling pad. Also of note is the fact that there is very little shadow to the left edge of the cushion. If you compare this to other objects that have some height they all have shadows casting to the left. To me this suggests that the wood to the left of the cushion is level or very close to being level to the seat cushion.

Also note the arrows pointing to the screws in the wood. This seems to make sense with the drawing above.