From http://hum.amu.edu.pl/~rafalp/HERM/dmanus.html:
London, British Library: Sloane MS. 2599, art. 1. A partial transcription of 'Liber mysteriorum sextus et sanctus' in at least two different hands. One of them may be Ashmole's.
From http://www.levity.com/alchemy/britlib1.html:
MS. Sloane 2599.
Paper. Folio. 49 folios. Beginning of 18th Century.
1. A work in cipher, entitled 'Liber misteriorum sextus et sanctus' with tables [Parts of Dr Dee's work on Angels, copied from MS. Sloane 3189.] ff. 1-45.
2. Preface and notes by John Michael Faustius, to the 'Introitus apertus ad occulsum Regis Palatium, a Philaletha', discussing the subject of the real name and the country of the author Philalethes. ff.46-49.