What is Mirror Des Justices?

Legal Definition
The Mirror of Justices, a treatise written during the reign of Edward II. Andrew Horne is its reputed author. It was first published in 1642, and in 1768 it was translated into English by William Hughes. Some diversity of opinion seems to exist as to its merits. Pref. to 9 & 10 Co. Rep. As to the history of this celebrated book see St. Armand's Hist. Essays on the Legislative power of England, 68, 59.
-- Bouviers Law Dictionary