Background
Isselt was born between 1530 and 1540 in Amersfoort in the Lordship of Utrecht.
Isselt was born between 1530 and 1540 in Amersfoort in the Lordship of Utrecht.
He studied at the University of Leuven and became a priest.
He is best known as the compiler (under the pseudonym "Doctorate M Jansonio") of the first Mercurius Gallobelgicus, a semi-annual overview of important current events. During the Dutch Revolt he went into exile in Cologne, where he became an active writer, recording contemporary events from a Catholic perspective. He died in Hamburg on 17 October 1597.
He also edited the works of Louis of Granada for publication in Cologne, translating some from Spanish or Italian into Latin. usque ad septembrim anni 1586 (Cologne, Gottfried von Kempen, 1586).