A transcript made in 1610 by John Jones, Gellilyvdy, of a treatise on astronomy from a manuscript in the hand of Richard ap Sion, Llangynhafal, Denbighshire. John Jones has given it the title of 'Llyfr Sion ap Wiliam ap Sion ap Wiliam ap Sion ap Dafydd ap Ithel Vychan o Astronomi neu wybryddiaeth'.