Sentence:  As for the planet high up to the right in the sky, I have not managed to ascertain whether it is a product of the Pythagorean <WSD>Antiearth</WSD>, or of the sentiment laid in my soul by the radiation of Planck's 'Black Body' 
Meaning of the word marked with <WSD> tags:  A hypothetical twin planet to earth, proposed by the Pythagoreans, which cannot be seen from earth.