Wushu Tao
(https://www.wushu-tao.com)
Writing sheet of the characters : - wú jí 无极 (Etat de vide, précédant l'interaction entre le YIN et le YANG)
   
For more informations about these characters and their pronunciations, consult this page :
https://www.wushu-tao.com/page_ac_liste_car.php