On the Nature of Things (De rerum natura) by Lucretius is a fascinating glimpse at the foundation of scientific thought from the 1st century BC. I just finished reading it; it's an interesting mix of combining logic with observation to try to understand physical phenomenon. He gets many things wrong from a modern understanding of physics; but there are many prescient ideas including the idea of indivisible particles of matter and that much of what we interpret as "solid" is primarily composed of empty space.