3 4 4 ▁and ▁possibly ▁by ▁ 1 3 4 0 . ▁His ▁mag num ▁op us ▁was ▁a ▁series ▁of ▁treat ises ▁known ▁as ▁the ▁Liber ▁calculation um ▁(" Book ▁of ▁Calcul ations "), ▁written ▁c . ▁ 1 3 5 0 , ▁which ▁earned ▁him ▁the ▁nick name ▁of ▁The ▁Calcul ator . ▁ ▁Robert ▁Bur ton ▁( d . ▁ 1 6 4 0 ) ▁wrote ▁in ▁The ▁An atom y ▁of ▁Mel anch oly ▁that ▁" Scal iger ▁and ▁Card an ▁adm ire ▁Su isset ▁the ▁calcul ator , ▁qui ▁p ene ▁mod um ▁excess it ▁hum ani ▁ingen ii ▁[ wh ose ▁tal ents ▁were ▁almost ▁super human ] ". ▁ ▁Gott fried ▁Le ib n iz ▁wrote ▁in ▁a ▁letter ▁of ▁ 1 7 1 4 : ▁" Il ▁y ▁a ▁eu ▁aut ref ois ▁un ▁Suisse , ▁qui ▁av oit ▁math ém at isé ▁dans ▁la ▁Sch ol ast ique : ▁ses ▁O uv rages ▁sont ▁peu ▁conn us ; ▁mais ▁ce ▁que ▁j ' en ▁ai ▁vu ▁m ' a ▁par u ▁prof ond ▁et ▁consid éra ble ." ▁ ▁(" There ▁was ▁once ▁a ▁Suisse , ▁who ▁did ▁mathematics ▁belonging ▁to ▁sch ol astic ism ; ▁his ▁works ▁are ▁little ▁known , ▁but ▁what ▁I ▁have ▁seen ▁of ▁them ▁seemed ▁to ▁me ▁prof ound ▁and ▁relevant .") ▁ ▁Le ib n iz ▁even ▁had ▁a ▁copy ▁of ▁one ▁of ▁Sw ines head ' s ▁treat ises ▁made ▁from ▁an ▁edition ▁in ▁the ▁Bibliothèque ▁du