《太平广记·卷二百三十八·诡诈》
其实，唐同泰先在白石上凿刻上字，再用紫色的石末和药嵌在字上面。
乃是将石凿作字，以紫石末和药嵌之。
In reality, Tang Tongtai first engraved the characters on the white stone, then inlaid the characters with purple stone powder and medicine.