梁张汝珍，南阳人，居南岳。遇神仙授明镜之道，曰：照物理者天也，照物形者镜也。天之道，以清镜之体，以明人能存。天清镜明，澄心静神，则至道成矣。处其室则白自生，定其心则道自生。
Chang Ju-chen of the Liang dynasty was a native of Nan-yang. He lived on the Nan Yo，and on one occasion met a fairy who gave him the principle of Clear Glass，which is this，What reflects or illuminates the nature or principle of things is Heaven: what reflects the form or shape of things is glass. The principle of Heaven is purity，or glass clearness. A man who possesses the purity of Heaven and the clearness of glass can wash his heart，quiet his spirit，and achieve becoming a fairy.