Claim: By the time of Diocletian, a Roman emperor from 284 to 305, the domes had already gained their symbolism of superiority.
Evidence: Diocletian (/ˌdaɪ.əˈkliːʃən/; Latin: Gaius Aurelius Valerius Diocletianus; born Diocles; 22 December c. 244 – 3 December 311) was a Roman emperor from 284 to 305. The first time Diocletian's whereabouts are accurately established, in 282, the Emperor Carus made him commander of the Protectores domestici, the elite cavalry force directly attached to the Imperial household – a post that earned him the honour of a consulship in 283.