Down the primrose path

What is the orgin and meaning of "To be lead down the primrose path"?

This is what I found so far:

Shakespeare's Hamlet. Ophelia: Do not, as some ungracious pastors do, Show me the steep and thorny way to heaven, Whiles, like a puff'd and reckless libertine, Himself the primrose path of dalliance treads, And recks not his own rede.

Shakespeare also used it in Macbeth, where the porter speaks of "treading the primrose path to the everlasting bonfire". This implies that in his day it was already a standard metaphor for the easy, pleasant self-indulgent way, as opposed to the "rocky road of righteousness".