Robert Temple's book is a stiletto in the side of modern, self-righteous "science" which only sees ancient knowledge as primitive fantasy.
Temple shows that there are hundreds of crystal lenses in museums around the world, which have been labelled as mere "ornaments," or such baubles. The emperor Nero wore an emerald lens to see gladiator fights, to aid his faulty vision. Such lenses could certainly have provided deeper views of the heavens than today's scientists allow for.
But beyond the mere existence of these lenses, Temple delves into the Pythagorean notion that the Sun itself is but a reflection (or refraction) of a larger Central Fire, at the core of the Universe.
With today's knowledge of the Galactic Center, which houses a humongous Black Hole, such a notion hints that the Ancients may indeed have known much more about cosmology than we have given them credit for.