From the Tseshaht and the father of Frank Williams, William provided some key historical Tseshaht accounts such as ;
- The Origin of the Tseshaht and the Story of Tlatlaaqokw’ap and Taaposhinis dictated by William, Oct. 17 and 20, 1913, to Edward Sapir,
- How the Hikoolthath Explored the Head of Alberni Inlet. This story belongs to William, Big Fred, Frank Williams, William’s sister.
- In 1913 William identified 20 Tseshaht fishing tutuupata on the Somass River. He provided valuable information on kitsaksu7is formerly given as a dowry to the first Hikoolthath man who is said to have found Alberni Inlet. The ownership rights were held by William, and passed to his son, Frank Williams. And history of other tupaati sites (hereditary right or privilege) such as gathering clover roots.
William’s name Yaap’inat was from his father’s uncle who was a Tseshaht living at Ts’ishaa.
William carved many significant cultural artifacts now held by the Canadian Museum of Civilization such as four model house posts and ritual seal clubs. He told many spiritual mountain stories on spiritual objects which can give power for various purposes. Provided some key in depth accounts of seating at feasts and provide key accounts of Tseshaht amalgamations such as Maqtliaht. William also provided valuable song data such as lullaby and tamaa (social) songs. He provided whalers accounts. William’s wife held a high place among the Huupach’as?ath.