Most grammars of English published in Britain during the 19th century are dull ... There were a great many grammars, issued in very large numbers. They were repetitive; many were merely commercial ventures, scholastically naive ... The vast number of grammars contrasts with the uniformity of their contents. Of all the subjects in the school curriculum English grammar was the most rigid and unchanging ... Teachers had insisted, for two centuries, on writing grammars which added little or nothing to what had gone before.
- Michael, I. (1991), "More than enough English grammars", in G. Leitner, English Traditional Grammars. Amsterdam: John Benjamins, 11-26.
However, a radical exception to the bunch was that by the English philologist, phonetician and grammarian Henry Sweet. Among other works ranging through Anglo-Saxon, Icelandic and phonetics, his 1891 A New English Grammar is unusual in taking a robust descriptivist stance:
... it must be borne in mind that the rules of grammar have no value except as statements of facts: whatever is in general use in a language is for that very reason grammatically correct.
Pullum & Huddleston's 2005 A Student's Introduction to English Grammar comments:
The prescriptive grammars of the twentieth century might have been more useful if they had paid more attention to Sweet instead of simply trying to transmute personal prejudice into authority.
Sweet's work is commemorated by The Henry Sweet Society for the History of Linguistic Ideas, and all his works are online at the Internet Archive (search on "Henry Sweet"), including A New English Grammar (Vol 1 / Vol 2). His 1890 A Primer of Spoken English (adapted from his 1885 Elementarbuch des gesprochenen Englisch) is particularly interesting as the first phonetically notated description of educated Southern English (what's now called Received Pronunciation). It contains observations from 120 years ago of features of RP, such as that of intrusive/linking r below, that are commonly thought to be recent:
The fact is that the statements of ordinary educated people about their own pronunciation are generally not only valueless, but misleading. Thus I know as a fact that most educated speakers of Southern English insert an r in idea(r) of, India(r) office etc. in rapid speech, and I know that this habit, so far from dying out, is spreading to the Midlands; and yet they all obstinately deny it. The associations of the written language, and inability to deal with a phonetic notation, make most people incapable of recognizing a phonetic representation of their own pronunciation.
- A Primer of Spoken English, 1890, Preface, page viii.
Sweet's expertise in philology and accents, plus highly abrasive personality, made him a strong influence in the character of Henry Higgins in Shaw's Pygmalion. The preface to Pygmalion - A Professor of Phonetics - describes Sweet as a talented scholar with a major chip on his shoulder about academia, and especially Oxford.
Pygmalion Higgins is not a portrait of Sweet, to whom the adventure of Eliza Doolittle would have been impossible; still, as will be seen, there are touches of Sweet in the play. With Higgins's physique and temperament Sweet might have set the Thames on fire. As it was, he impressed himself professionally on Europe to an extent that made his comparative personal obscurity, and the failure of Oxford to do justice to his eminence, a puzzle to foreign specialists in his subject. I do not blame Oxford, because I think Oxford is quite right in demanding a certain social amenity from its nurslings (heaven knows it is not exorbitant in its requirements!); for although I well know how hard it is for a man of genius with a seriously underrated subject to maintain serene and kindly relations with the men who underrate it, and who keep all the best places for less important subjects which they profess without originality and sometimes without much capacity for them, still, if he overwhelms them with wrath and disdain, he cannot expect them to heap honors on him.
Actually there are more than "touches" of Sweet in Pygmalion; Bertrand M Wainger's paper Henry Sweet - Shaw's Pygmalion (Studies in Philology, Vol. 27, No. 4, Oct., 1930) notes strong similarities:
It is evident that Shaw took Sweet as a model for some of the major lineaments of the portrait of the Professor Higgins of the play. It was Sweet who invented the Broad Romic system of phonetic notation; it was Sweet who sent postcards in that script and in his shorthand script to his friends; it was Sweet who was able to pronounce distinctly seventy-two vowel sounds. Sweet would often turn his back on a group of speakers and jot down a phonetic record of their conversation; Sweet was engrossed in his studies - as is Professor Higgins - to the exclusion of the social amenities; and Sweet alone, in England, was sufficiently the master of the science of phonetics to have been able to transmute Liza into Miss Doolittle.
Sweet's grievance may well have been to do with getting a fourth-class degree from Oxford (effectively a "fail"). Accounts of him in later life variously describe his "cantankerousness and embittered attitudes" (page 421, The History of the University of Oxford: The Nineteenth Century, Volume 7, Part 2) and his "embittered isolation, which developed virtually into a form of persecution mania in the years before his death in 1912" (page 48, The real Professor Higgins: the life and career of Daniel Jones). See Against the establishment: Sidelines on Henry Sweet for more of the same.
It's tempting to suspect that Sweet's emphasis on descriptivism was somewhat driven by his hatreds: its opposite, prescriptivism, is heavily associated with the Establishment (a point argued by Geoffrey Pullum in the paper Ideology, Power and Linguistic Theory). Nevertheless, Sweet's contribution to the study of linguistics was immense, paving the way to the "Great Tradition" of 20th century descriptive linguistics; he was an inspiring teacher for those who weren't on his hate list, and Otto Jespersen (see previously) was one of his pupils.