I thought Judy Collins sang it unaccompanied, but of course Joe is right. I must have been thinking of the Priscilla Herdman recording. At one time it seemed to me that Herdman was on a mission to record everything Collins had ever sung (not that there's anything wrong with that).

It's also on a CD by the Australian group, Quintessence - and that one is an unaccompanied trio.