One of the most prolific and influential (but also somewhat hidden) foreign (i.e. non-Portuguese) Jesuits who arrived in Coimbra’s Colégio das Artes to teach mathematics, and who left most traces of his stay there was the Belgian Antoine Thomas (Mauricio 1935: 196-197). Thomas was born in Namur (Belgium), at the frontiers of the Spanish Low Countries with France, on 25 January 1644, in a family of administrative nobility – very similar to the milieu in which several other Jesuit missionaries of the previous generation were born, viz. Ferdinand Verbiest (1623-1688), François de Rougemont (1624-1676) and Philippe Couplet (1622 – 1693), the two former of them well know in Coimbra too. Since his early education, he was a pupil of Jesuit institutions: first in the Jesuit college of Namur (1652 – 1660) (Sauvage, 2017); since 8 Sept. 1660 in the Novitiate of the Provincia Gallo-Belgica in Tournai (1660-1662); in 1662-1664 as a philosophus in Douai, in 1665 in Lille (“Insulis”); in 1666-1667 again in Namur as a professor of syntaxis; 1668-1670 as a professor of poesis in Huy; in 1670-1671 as a ‘rhetoricus’ in Tournai again; theology studies in Douai (1671-1675), and afterwards Professor of philosophy in the Jesuit college of Marchiennes, one of the Jesuit institutions in the same city (1675-1677) (Hermans, 2017). Nowhere during this educational trajectory there is an explicit trace of specialized, let alone curricular studies in mathematics, which, as in many other cases, was therefore the object of his own free preference and of his “studium privatum”, started in view of his application for China, as we learn from his own testimony in his letter of 24 May 1671 (JS 148, f. 13); one could suppose that Father Michel Sénéchal (1606-1673) and Alexandre de Bonmont (1632-1718), both Jesuits with a mathematical profile were to some extent involved in this ‘private study’, but only in the case of De Bonmont a relation with Thomas is proven, though by a later correspondence (see infra).