Nefesh HaChayim, Reb Itzele's Long Annotation

And though how the internals of the elements in the person’s soul-Neffesh combine is not perceptible by the senses in any way, however when the light of their combination shines upon their vessel—the element of dust (the root of the body)—then the body expresses outwardly the powers of the three “mothers”—aleph, mem, shin451See Sefer Y’tzeera— each according to its effects, as explained in Zohar Va-eira mentioned previously. And the power of the combination of the three elements—fire, wind and water—they [emphatic] are the roots from which are drawn all of the body’s actions, but they are hidden and are not perceived.