[2007] Karlowa Rechtsgesch. i. p. 539.
[2008] Coins of 16 B.C. exist (Eckhel vi. 105) with the inscription “s. p. q. R. imp. Cae(sari), quod v(iae) m(unitae) s(unt) ex ea p(ecunia) q(uam) is ad a(erarium) de(tulit)”; cf. Vita Pert. 9 “aerarium in suum statum restituit. Ad opera publica certum sumptum constituit. Reformandis viis pecuniam contulit.”
[2009] Frontinus de Aquaed. 100 and 104.
[2010] Dio Cass. lvii. 14.
[2011] Tac. Hist. i. 58.
[2012] Cic. pro Caec. 20, 57.
[2013] Tac. Ann. iv. 6 “intra paucos libertos domus.”
[2014] Tac. Hist. i. 58 “Vitellius ministeria principatus per libertos agi solita in equites Romanos disponit.” In Otho’s reign we find a mention of Secundus the rhetor ἐπὶ τῶν ἐπιστολῶν γενόμενος (Plut. Otho 9).
[2015] The evidence for Hadrian’s change is mainly epigraphic. See Hirschfeld Verwaltungsgesch. i. p. 32. Two instances of it are found in Vita Hadr. 22 “ab epistulis et a libellis primus equites Romanos habuit.”
[2016] Dio Cass. lii. 25.