Aristarchus of Samos calculated the distances and size of both the moon and the sun some time between 300BC and 200BC. These distances and, at least for the sun, the sizes are so mind boggling they continue to awe us to this day.
How were these quantities perceived by ancient astronomers and thinkers of the day? I know that question is open ended as far as time goes, but I'm not sure just how much exists on it and I'd really be curious to hear from any era's perspective.
This sounded fishy to me, and according to what I could find on the subject, he was only able to calculate the distance to the sun in terms of earth-moon distances, and he was able to calculate the size of the sun in terms of moon-sizes, but while he knew the relative proportions of these things, he was unable to calculate them in absolute terms. Still an impressive feat, but as someone who knows a bit about physics and astronomy, I don't see how it would have been possible at that time for him to have known the absolute sizes and distances.