Qing dynasty "palace memorials" were documents submitted to the emperor by officials, some reporting local affairs, and others expressing gratitude to the emperor. Originated with the Kangxi Emperor, the memorial system was developed further under the Yongzheng Emperor, and became firmly established during the Qianlong Emperor's reign as an important channel of communication between the emperor and his officials. With contents covering state and military affairs, matters of the imperial household, local affairs, the appointment and recall of officials, finance, agriculture, matters of custom, and education, the memorials are important historical documents for the study of major events of the Qing dynasty. The National Palace Museum holds in its collection a large quantity of Qing dynasty palace memorials. Annotations in vermilion ink left on the memorials by successive emperors give an indication of their personalities and styles of governance and also reveal their accomplishments in calligraphy.