Baynes's most consequential and lasting work was her English translation of Richard Wilhelm's German I Ching, undertaken at Jung's own suggestion and published by the Bollingen Foundation in 1950 with a foreword written by Jung himself. Rather than working from the original Chinese, she translated Wilhelm's German rendering directly, carrying his interpretive choices and extensive commentary into English essentially intact, a second layer of translation that nonetheless became, and has remained, the English edition most widely read and cited in the West.
Her earlier translation work on Wilhelm and Jung's jointly annotated Chinese alchemical text The Secret of the Golden Flower, published in 1931, had already established her as Wilhelm's principal English voice before the larger I Ching project began. Because Wilhelm had died in 1930, Baynes's I Ching translation carried his scholarship to its widest audience only after his own death, making her, in practical terms, the person most responsible for how English readers have encountered his work at all.
The Bollingen edition she produced went through multiple later printings and remained the dominant English I Ching for decades, reaching well beyond the academic and Jungian readership it was originally aimed at and into the broader countercultural interest in Eastern thought that grew through the 1960s and 1970s. Newer English translations working directly from the Chinese have since appeared, but Baynes's edition, carrying Wilhelm's German and Jung's foreword together, remains in print and is still frequently the first I Ching many English language readers encounter.