Sentence:  Following the reign of Scptimius Severus (193-211), the emperor's patrimonium, his personal properties, was merged with a new department, the ratio privata (private  accounts) headed by the magister rationis summae privatae at the <WSD>tricenarian</WSD> level. 
Meaning of the word marked with <WSD> tags:  The highest rank and pay grade for prefectures in Ancient Rome