Sui (581-618) & Tang (618 - 907) Dynasties
According
to a Tang Dynasty record, Empress Wu Ze Tien (623-705) issued an order to change
the name “Xi”, which was up until then used for imperial seals, to “Bao”
(literally means treasure). She avoided the word ”Xi” because it was close
in pronunciation to ”Si” (death). Later when Emperor Tang Zhong Zong resumed
the throne in 705, he changed the name for imperial seals back to Xi. Since then
Xi and Bao were used interchangeably from the Sung and Yuan Dynasties to the
Ching Dynasty.
The
calligraphy style and script method of the Tang Seals were quite different from
the Han Seals.