《太平广记·卷一百三十五·征应一》
元吉派使者献石，文字非常清楚好像龟的形状，看见的人都感到十分奇怪。
元吉遣使献之，文字暎澈，宛若龟形，见者咸异焉。
Yuanji sent messengers to offer the stone, the characters on it were very clear and looked like the shape of a turtle. Anyone who saw it was very surprised.