Now, of course, she knew what seeing was, and for the first time she was aware of the real sizes of things.

Poor man measures all things by the size of his own foot.

He looks complacently at the print of his boot in the mud, and notices that the ant which he crushed was not nearly as big as his foot, therefore the ant does not matter to him.

He also notices that those same feet of his would not be able to walk to the moon within a reasonable time, therefore the moon does not matter to him.
But Sarah Brown had disappeared, and therefore could not measure anything.

The spider strode from hill to hill, with the wind rushing through the hair on his back.