In A Box of Rain, Robert Hunter's collected Grateful Dead lyrics, the poet comments on this song:
Phil Lesh wanted a song to sing to his dying father and had composed a piece complete with every vocal nuance but the words. If ever a lyric "wrote itself," this did—as fast as the pen would pull.
The book A Box of Rain (Penguin Books, 1990, 1993 ISBN 0 14 01.3451 4) contains the lyrics to all the songs Hunter wrote in collaboration with various members of the Grateful Dead (Jerry Garcia, Ron McKernan, Phil Lesh, Bob Weir, Bill Kreutzman, Mickey Hart, Keith Godchaux) between 1965 and 1993. It's an encyclopedic reference liberally flavored with the writer's comments, such as the above.