Physiomathematica

Placidus's Physiomathematica is a 17th-century Latin work in which the scholar-astrologer Placidus set out mathematical and astronomical foundations for his astrological methods, notably the quadrant house system later known by his name.

The text aimed to reconcile astrology with contemporary scientific and ecclesiastical scrutiny by offering rigorous mathematical justification for techniques such as parallels and house division.

Its dense and technical material influenced later astrologers but also attracted controversy, contributing to the banning of Placidus's works by the Inquisition.

A second edition (1675) edited by his students added an appendix that introduced the concept of equidistances, the historical origin of modern midpoints.