The Harleian Miscellany was a collection of material from the library

Library

In a traditional sense, a library is a large collection of books, and can refer to the place in which the collection is housed. Today, the term can refer to any collection, including digital sources, resources, and services...

 of the Earl of Oxford

Earl of Oxford

Earl of Oxford is a dormant title in the Peerage of England, held for several centuries by the de Vere family from 1141 until the death of the 20th earl in 1703. The Veres were also hereditary holders of the office of master or Lord Great Chamberlain from 1133 until the death of the 18th Earl in 1625...

 collated and edited by Samuel Johnson

Samuel Johnson

Samuel Johnson , often referred to as Dr. Johnson, was an English author who made lasting contributions to English literature as a poet, essayist, moralist, literary critic, biographer, editor and lexicographer...

 between 1744 and 1753. Its proper title is A Collection of Scarce, Curious, And Entertaining Pamphlets And Tracts, as well In Manuscript As In Print, Found In The Late Earl Of Oxford's Library, Interspersed With Historical, Political, And Critical Notes.

Provenance

The "late Earl of Oxford" whose library was the source of the texts could refer either to Robert Harley, 1st Earl of Oxford and Mortimer

Robert Harley, 1st Earl of Oxford and Mortimer

Robert Harley, 1st Earl of Oxford and Earl Mortimer KG was a British politician and statesman of the late Stuart and early Georgian periods. He began his career as a Whig, before defecting to a new Tory Ministry. Between 1711 and 1714 he served as First Lord of the Treasury, effectively Queen...

 (died 1724), or to his son, Edward Harley, 2nd Earl of Oxford and Mortimer (died 1741). A passage at the beginning of the first volume emphasizes the role of Robert Harley, the first earl, in the creation of the library:

There can be no Objection against the Prefixing the reasons for Creating the Right Honorable Robert Harley, Esq., a Peer of Great-Britain, and Earl of Oxford; especially, as the valuable Collection, intended to be published in this Form, was made by the Greatness of his Knowledge in all Branches of Learning, and at the vast Expence of that noble Family. ...his Library consisted of more than 100000 different Authors: He, I say, cannot be denied the first Place in this Miscellany, which esteems it an Honour to bear his Name.

Edward Harley, the second earl, who had died only a few years before The Harleian Miscellany was published, was also a bibliophile who had greatly expanded the library.