I have not found it in his monumental 1983 book,
Agni: The Vedic Ritual of the Fire Altar, nor in his more popular 2008 book,
Discovering the Vedas. I thought it might be in his 1961 book,
Nambudiri Veda Recitation, but I did not find it there, either. Incidentally, when I could not at first find my copy of this book, I searched the web for it, but did not find a digital copy. So when I later found my copy, I scanned it, and I will ask our digital expert Lubomir Ondra
čka to upload it to
archive.org.
Colorado, U.S.A.