One of the books given in the references is actually available in it's entirety [1] and appears to be quite good. Chapter 6 covers Seki, Chapter 7 is about his

One of the books given in the references is actually available in it's entirety [1] and appears to be quite good. Chapter 6 covers Seki, Chapter 7 is about his contemporaries and western influences (or lack there-of), and Chapter 8 is about the 'yenri', which is the Calculus system in question. [1] https://books.google.com/books?id=J1YNAAAAYAAJ https://books.google.com/books?id=J1YNAAAAYAAJ