Musaeum Clausum (Latin for Sealed Museum), also known as Bibliotheca abscondita, is a tract written by Sir Thomas Browne first published posthumously in 1684. The book contains short descriptions of supposed, rumoured or lost books, pictures, and objects. The subtitle describes the book as an inventory of remarkable books, antiquities, pictures and rarities of several kinds, scarce or never seen by any man now living. The tract's date is unknown: however, an event from the year 1675 is cited.
Like Pseudodoxia Epidemica, Musaeum Clausum is a catalogue of doubts and queries, only this time, in a style that anticipates Jorge Luis Borges, a 20th-century Argentinian short-story writer who once declared: "To write vast books is a laborious nonsense, much better is to offer a summary as if those books actually existed."
Browne however was not the first author to engage in such fantasy. The French author Rabelais in his epic Gargantua and Pantagruel also penned a list of imaginary and often obscene book titles in his "Library of Pantagruel" an inventory which Browne himself alludes to in Religio Medici.
As the 17th century scientific revolution progressed the popularity and growth of antiquarian collections, some claiming to house highly improbable items grew. Browne was an avid collector of antiquities and natural specimens possessing a supposed unicorn's horn, presented to him by Arthur Dee . Browne's eldest son Edward visited the famous scholar Athanasius Kircher, founder of the Museo Kircherano at Rome in 1667, whose exhibits included an engine for attempting perpetual motion and a speaking head, which Kircher called his Oraculum Delphinium. He wrote to his father of his visit to the Jesuit priest's "closet of rarities".
Early museums such as Kircher's were private affairs, wooden arks or cabinets where antiquarians kept collections of curious objects. The intellectual collector of such curiosities was the forerunner of today's professional natural historian and scientist. Physicians in particular took an interest in natural history, one of the best known early collectors was Hans Sloane. Distinguished in medicine and science, Sloane was President of both the Royal Society and the Royal College of Physicians. The books and objects he collected, including those auctioned from the libraries of Thomas Browne and his son Edward in 1711, became the foundation of the British Museum.
The sheer volume of book-titles, pictures and objects listed in Musaeum Clausum is testimony to Browne's fertile imagination; however his major editors, Simon Wilkins in the nineteenth century (1834) and Sir Geoffrey Keynes in the twentieth (1924) summarily dismissed it. Keynes considered its humour too erudite and "not to everyone's taste." However, this minor work deserves to be better known for it allude to motifs and symbols from the worlds of Classical literature, the Bible and alchemy which fascinated Browne throughout his life and is therefore a 'snap-shot' in précis of the symbols which preoccupied him.
Browne's miscellaneous tract may also be read as a parody of the rising trend of private museum collections with their curios of doubtful origin, and perhaps also of publications such as the so-called Museum Hermeticum (1678) one of the last great anthologies of alchemical literature, with their divulgence of near common-place alchemical symbols and secrets.