Vitruvius
Marcus Vitruvius Pollio (born c. 80–70 BC, died after c. 15 BC) was a Roman writer, architect and engineer, active in the 1st century BC. He is best known as the author of the multi-volume work De Architectura ("On Architecture").
By his own description Vitruvius served as a ballista (artilleryman), the third class of arms in the military offices. He likely served as chief of the ballista (senior officer of artillery) in charge of doctores ballistarum (artillery experts) and libratores who actually operated the machines.
Read more about Vitruvius: Life and Career, Vitruvius' De Architectura Libri Decem (De Architectura), Roman Technology, Rediscovery, Lists of Names Given in Book VII Introduction, Legacy