The Holophusikon (or Holophusicon, also known as the Leverian Museum) was a museum of natural curiosities exhibited at Leicester House, on Leicester Square in London, England, from 1775 to 1786 by Ashton Lever.
Lever collected fossils, shells, and animals (birds, insects, reptiles, fish, monkeys) for many years, accumulating a large collection at his home at Alkrington, near Manchester. He was swamped with visitors, whom he allowed to view his collection for free, so much so that he had to insist that visitors that arrived on foot would not be admitted. He decided to exhibit the collection in London as a commercial venture, charging an entrance fee. Lever acquired a lease of Leicester House in 1774, converting the principal rooms on the first floor into a single large gallery running the length of the house, and opened his museum in February 1775, with around 25,000 exhibits (a small fraction of his collection) valued at over £40,000. The display included many natural and ethnographic items gathered by Captain James Cook on his voyages. Lever charged an entry fee of 5s. 3d., or two guineas for an annual ticket, and the museum had a degree of commercial success: the receipts in 1782 were £2,253. In an effort to draw in the crowds, Lever later reduced the entrance fee to half a crown (2s. 6d.), , and was constantly looking for new exhibits. He also set out his exhibits to impress the visitor, as well as (unusually) including educational information. However, he spent more on new exhibits than he raised in entrance fees. The collection was acquired by James Parkinson through a lottery in 1786, but continued to be displayed at Leicester House until Lever's death in 1788. Parkinson then moved the collection to a Rotunda at No. 3 Blackfriars Road, before it was dispersed in an auction in 1806. The museum took its name from its supposedly universal coverage of natural history, and was essentially a huge cabinet of curiosities. The British Museum and Catherine II of Russia both refused to buy the collection, so Lever obtained an Act of Parliament in 1784 to sell the whole by lottery. He only sold 8,000 tickets at a guinea each - he had hoped for 36,000 - and it was then broken up by a James Parkinson (not the famous doctor). It was displayed at Leicester House until Lever's death in 1788, at a reduced entrance fee of 1s., and Parkinson then transferred it to a Rotunda at No. 3 Blackfriars Road. Leicester House was then demolished in 1791. Parkinson sold the collection in lots by auction in 1806. Among the buyers of items were Edward Donovan, Edward Stanley, 13th Earl of Derby, and William Bullock; many items went to other museums, including the Imperial Museum of Vienna. The contents of the museum are unusually well recorded, from a catalogue of the museum created in 1784, and the sale catalogue in 1806, with a contemporary series of watercolours of its contents by Sarah Stone. Among the objects displayed was the large Viking silver thistle brooch from the Penrith Hoard, discovered by a boy in Cumbria in 1785. In 1787 a print of it was published, claiming that it was the insignia of the Knights Templar. It was bought by the British Museum in 1909 (M&ME 1909,6-24,2).