Kiparsky said there were no such lines in Shakespeare. However, there is at least one: "Give renew'd fire to our extincted Spirits" (Othello II 1), pointed out as an objection to Kiparsky's theory by Groves, Peter L. (1998), Strange Music: The Metre of the English Heroic Line, ELS Monograph Series No.74, Victoria, BC: University of Victoria, ISBN0-920604-55-2. Thus Hayes's characterization "vanishingly few" seems more accurate.
"The Ants Go Marching". National Institute of Environmental Health Sciences. National Institutes of Health. June 8, 2012. Retrieved April 7, 2017.
proquest.com
For a detailed discussion of the varied intonations possible in iambic pentameter, see Cooper, John R. (Fall 1997). "Intonation and iambic pentameter". Papers on Language and Literature. 33 (4): 392–421. reprinted with changes as the first chapter of Cooper, John R. (2009). "Iambic Pentameter". Wit's Voices: Intonation in Seventeenth-century English Poetry. University of Delaware Press. pp. 37–58. ISBN978-0-87413-059-1.
Hayes, Bruce (1989), "The Prosodic Hierarchy in Meter"(PDF), Phonetics and Phonology, Volume I: Rhythm and Meter, Academic Press, pp. 201–260, retrieved 2012-07-24