Complex sentence: We learn from Vitruvius that Satyrus and Phytheus wrote a description of their work which Pliny probably read, and wrote down these dimensions without thinking about the form of the building.
Split into simpler sentences: We learn from Vitruvius that Satyrus and Phytheus wrote a description of their work which Pliny likely read. Pliny likely wrote down these dimensions without thinking about the form of the building.