I read the following in C. S. Lewis, Miracles (page 77-8)
The immensity of the universe is not a recent discovery. More than seventeen hundred years ago Ptolemy taught that in relation to the distance of the fixed stars the whole Earth must be regarded as a point with no magnitude.
There was no reference given, but I assume this would be in the Almagest. However, I don't know where in that work (or elsewhere) Ptolemy discussed this. I want to read his explanation for that view.
Hence the question: Where did Ptolemy compare the Earth to the distance of fixed stars?