Some notebooks have recently been transferred, within Yale, from the Art Gallery to the special collections of Sterling Memorial Library’s Manuscripts and Archives. A snippet of the kind of content contained in the notebooks can be found here. These were donated by Dr. Konrad Tuchscherer of St. John’s University.
In principle, the text should be fairly straightforward to transcribe, following the Unicode code chart here for the Kikakui script of the Mende language. But there is enough variance between the manuscript and the encoding that it will take some extra efforts to ensure that an accurate transcription can be made. Please leave a comment if you have any competence in Mende or familiarity with the Kikakui script; I’d love to hear from you!