Miller, J.S.: The notched stick. Am. J. Phys.
23/3, 176 (1955). http://adsabs.harvard.edu/abs/1955AmJPh..23..176M
Laird, E.R.: A notched stick. Am. J. Phys.
23/7, 472 (1955). http://adsabs.harvard.edu/abs/1955AmJPh..23..472L
Scott, G.D.: Control of the rotor on the notched
stick. Am. J. Phys. 24/6, 464 (1956). http://adsabs.harvard.edu/abs/1956AmJPh..24..464S
Scott, G.J.: A mechanical toy: The gee-haw
whammy-diddle. The physics teacher 12, 614
(1982). http://adsabs.harvard.edu/abs/1982PhTea..20..614A
H. Joachim Schlichting, Udo Backhaus "Zur Physik der Hui-Maschine" Physik und Didaktik 16/3, 238 (1988). https://video.uni-muenster.de/imperia/md/content/fachbereich_physik/didaktik_physik/publikationen/hui_maschine.pdf
Leonard, R.W.: An interesting demonstration
of the combination of two linear harmonic vibrations
to produce a single elliptic vibration. Am.
Phys. Teacher (now: Am. J. Phys.) 5, 175 (1937). http://adsabs.harvard.edu/abs/1937AmJPh...5..175L
Can't guarantee these are the exact six he means! The same concept is being applied or suggested for micro and nano machines. For example "The rotation of the added molecule would then resemble that of a well-known children's toy in which a propellor rotates at the end of a rubbed notched stick." A.M. Stoneham The challenges of nanostructures for theory
Bonus references:
Scarnati & Tice, "The Hooey Machine", Science Activities: Classroom Projects and Curriculum Ideas, vol. 29, Issue 2, pages 30-35 (1992) http://www.tandfonline.com/doi/abs/10.1080/00368121.1992.10113024?journalCode=vsca20#.U0H43xuPLmQ
J. Satonobu, S. Ueha and K. Nakamura, "A Study
on the Mechanism of a Scientific Toy 'Girigiri-
Garigari'," Jpn. J. Appl. Phys., 34, Part 1(5B):
2745-2751, 1995. http://iopscience.iop.org/1347-4065/34/5S/2745
Maybe the mention of Feynman is just Feynman's Ratchet