The much-cited passage by Ben Jonson is also the foundation of Sweet's (1888) opinion on the pronunciation of early Modern English /r/ (trilled initially, untrilled in rhyme positions): R is the Dogs letter, and hurreth in the sound; the tongue striking the inner palate, with a trembling about the teeth.
However, it may appear odd that there should be no doubt about this particular report while on the same page Sweet rejects Cooper's testimony to the effect that final /r/ was trilled: But here the mention of the vibration seems to be nothing but a part of the traditional definition of r.
a change in the nature of r from a point-trilled consonant to the PresE pointfricative, which has strong guttural quality and is closely allied to the vowel [[??]]; but in intervocalic position it commonly remained either a trilled consonant or the PresE 'flap' [r] Dobson 1968:945 [[section] 370]).
(7) A more cautious opinion is expressed in his Anglo-Saxon Primer: r initially was probably trilled, as in Scots: roed 'advice', ridan 'ride'.