The Bible.
Yes, it's true.
It is the perfect thickness to go under my heel so that I can run the pedal with the front part of my foot. Else my foot cramps up.
BTW, it is not the only Bible we have in the house; this one is an older one that gets little use. If someone needs this particular version, they can find it just as easily under my sewing machine as they can on the bookshelf!