After the reign of Marcus Aurelius (according to Mommsen) the equites were divided into: (a) viri eminentissimi, the prefects of the praetorian guard; (b) viri perfectissimi, the other prefects and the heads of the financial and secretarial departments; (c) viri egregii, first mentioned in the reign of Antoninus Pius, a title by right of the procurators generally.
The secretarial class consisted of six categories: the nishanjis, the defterdars, the reis, the defter emini, the shakk-i-sani (or second class) defterdars and the shakk-i-salis (or third class) defterdars.
The chief official of the lan is the landshi fding, under whom are secretarial and fiscal departments.
It seems probable that he lived in the French embassy in some secretarial or tutorial position.
In any case Prosper was soon in Rome, attached to the pope in some secretarial or notarial capacity.