According to the internet, the Friar is referring to Juliet's parent that them crying is normal and natural, but since Juliet is in a better place, they should rejoice for the dead and that her soul is still pure when she goes up to heaven because she is young. Or, Natures tear meaning natural tears, merriment meaning happy. It is natural to cry over the death of a child but they should be happy she is going to be in a better place.
One key difference between the critical acclaim received by Edgar Allan Poe and that received by Stephen King is that acknowledgement of Poe's skill came primarily after his death, while King has received numerous awards during his lifetime.
