"A Survey of Meillionydd Estate in the Hundred of Lleyn and other places in the County of Carnarvon The Property of S.r Robert Howel Vaughan Bart. Survey'd in the Years 1792 and 1793 by William Williams of Llandegai, and Assistants."

The Meillionydd estate can be said to have been founded by Arthur Williams, M.A., one of the younger sons of Cochwillan; it remained in the hands of his descendants till the sole heiress, heiress both to the Meillionydd land in Llyn and the Ystumcolwyn lands in co. Montgomery, was married in 1765 to Robert Howel Vaughan [afterwards Sir. Roberts], who ultimately succeeded to the nnau-Hengwrt estate (over four hundred papers bearing upon the Meillionydd lands are in this Archive, Nannau Manuscripts). The surveyor, William Williams, was one of the best known professional men in North Wales in his time - devoted servant to Richard [first] Lord Penrhyn. umpire and arbitrator in frequent demand, author of the "Observations on the Snowden Mountains" etc. This particular survey is done in his best style. The work of his "assistants" can be easily known by the script, while the Bryngwyn survey, co. Mont., between pp. 102-3 was added in 1825, eight years after his death.

Another catalogue description can be found here https://archiveshub.jisc.ac.uk/data/gb222-bmssmeill