Together with two other German-speaking members of the Accademia, Giovanni Faber and Theophilus Müller, he worked on the encyclopaedia of botany Rerum medicarum Novae Hispaniae Thesaurus which had been begun decades before by Francisco Hernández de Toledo and purchased, incomplete, by Federico Cesi.
The founder of the Jesuit mission in China, Matteo Ricci, had sent his colleague Nicolas Trigault back to Europe to search out new missionaries who could share the most advanced scientific ideas with the Chinese.
[7] In April 1618, Schreck sailed from Lisbon with a group of Jesuits Trigault had assembled, including Giacomo Rho and Johann Adam Schall von Bell.
There, probably in collaboration with a Christian convert named Li Zhizao,[13] he wrote Taixi renshen shuogai (An Outline of Western Theories of the Human Body), based on Theatrum anatomicum by Caspar Bauhin.
[4] For help in this task, Schreck wrote for advice to Johannes Kepler who replied in 1627, explaining how predictions could be improved by using an elliptical model for the Moon's orbit,[17] and enclosing a copy of his new Rudolphine Tables.
In advance of the solar eclipse of 21 June 1629 over Beijing, Schreck and Nicolò Longobardo competed with Chinese astronomers to predict the timing with the greatest accuracy.
Schall also published a manuscript by Schreck containing much of his knowledge of astronomy and related mathematics, called Ce tian yue shuo (測天約說) (Brief Description of the Measurement of the Heavens).
[7] Schall likewise revised and published two works by Schreck on trigonometry, Da ce (大測) (The Great Measurement) and Ge-yuan ba-xian biao (割圓八線表) (A Table of Eight Lines),[3] the latter together with Rho.