Lewis Short
rătĭōcĭnātor (noun M) : id.
* A reckoner, computant, accountant, i. q. calculator.
* Lit., Cic. Att. 1, 12, 2; Col. 3, 3, 7; Dig. 14, 4, 5, § 16.
* Trop.: ut boni ratiocinatores esse possimus et addendo deducendoque videre, quae reliqui summa fiat,Cic. Off. 1, 18, 59; Aug. Civ. Dei, 21, 5.
Charlton T. Lewis, Charles Short, A Latin Dictionary