There aren't any clues, really. You have to sort of figure it out with reasoning. or luck.
BUT, I discovered after finding the right combination that there's a way to see the right combo which is unintentional. Stand between the giant wheel and the lever, facing the wheel with your back right up against the lever. Then go into the free-moving camera mode (press the right mouse button). Then move the mouse around so that you are looking up at your character from behind. the clipping issues in the game allow you to see the bottom of that white block of stone on the lever stand, and it has the correct wheel pattern on it.
Of course, this isn't the intended way to see the pattern, but there it is.
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