Henry Peacham (flor. 1577) was the father of the Henry Peacham who wrote the Compleat Gentleman. The quotation below is from the second and augmented edition of the Garden of Eloquence (1593). The first edition of 1577 contains no mention of Spenser.
From The Garden of Eloquence Conteining The Most Excellent Ornaments, Exornations, Lightes, flowers, and formes of speech (1593), p. 15 (under Onomatopeia):
Touching this part I will refer the Reader to Chaucer & Gower, and to the new Shepherds calender, a most singular imitation of ancient speech.