On May 22, 1812, Lady Caroline Lamb writes to Annabella Milbanke, who in turn writes on it "a letter of Lady Caroline Lamb to me—1812—very remarkable." Part of Lady Caroline's letter reads:
[M]y beautiful Rhapsodies like every thing else I do—burst forth on every event to perish with it—witness all the Elegies I have written since five years old for every dog cat monkey & squirrel that left this goodly world & where is the young Lady who has not addrest Cynthia bright Goddess—Hygea—innocent Doves—Lambs playing on the Green—the return of Spring—the Fall of the Leaf—a cow ruminating after its dinner & all the other Images that awaken sympathetic emotions in the youthful heart.”Notes
The extract above is found in the article of Paul Douglass "Lord Byron’s Feminist Canon: Notes toward Its Construction" which can be found here. It has following notation: Lady Caroline Lamb to Annabella Milbanke, 22 May 1812. Bodleian, Dep. Lovelace Byron 359.