Liber Officium Spirituum

Liber Officiorum Spirituum (English: The Book of the Office of Spirits) was a demonological grimoire and a major source for Johann Weyer's Pseudomonarchia Daemonum and the Ars Goetia. The original work (if it is a single work) has not been located, but some derived texts bearing the title have been found, some in the Sloane manuscripts, some in the Folger Shakespeare Library. Each version bears many similarities to each other and to the Pseudomonarchia Daemonum and the Ars Goetia; though they are far from identical.

Johannes Trithemius mentions two separate works (Liber quoque Officiorum, and De Officiis Spirituum), indicating that the text may have branched off by his time. Weyer, in his Pseudomonarchia Daemonum, lists his source as Liber officiorum spirituum.Thomas Rudd titles his copy of the Ars Goetia as Liber Malorum Spirituum.

The most detailed version is a direct but poor translation from English to Latin. This version was either copied or translated by Englishman John Porter in 1583. This version was owned by artist Richard Cosway. Upon his death in the 1820s, it passed hands to a bookshop owned by John Denley, bought by an occultist named George W. Graham on behalf of an Magical organization known as "the Society of the Mercurii." In the hands of the Mercurii, it came into the possession of Robert Cross Smith in 1822, who had John Palmer copy it. With Smith's death in 1832, the copy was passed on to Frederick Hockley. At some later date, Hockley acquired the first half of Porter's original manuscript, and attempted to compile both Porter's and Palmer's versions into a single version.

Sloane MS 3824 (from the mid-seventeenth century) features a number of elements from the Book of the Office of Spirits and is an early form of the Lemegeton. MS 3853 is titled The Office of Spirits, starts off nearly identical to more complete Porter version.

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