The oldest Daoist seals appear in the Eastern Han dynasty, growing in importance and complexity throughout the middle ages. In particular, the so-called Yue Seal had an enduring reputation in Daoist healing and exorcism, its transmission, reproduction, and transformation ranging from the Han to the Tang and Song. The preferred materials for Daoist seal-making were first stone and metal, and later wood notably wood struck by lightning. Various ritual rules applied to carving, including selecting auspicious dates and properly venerating and placing the seal.