Every episode of Fringe contains a hidden clue that foreshadows something in the next episode. In last Fringe episode "Back To Where You've Never Been", when Peter and Lincoln cross over to the alternate universe, there is a Mohonk Teahouse on the corner.
In the Fringe episode "Enemy Of My Enemy", David Robert Jones is found mining Amphilicite at the Mohonk Quarry.
AGENT FARNSWORTH: Of all the locations he was studying, the one with the most potential for Amphilicite is located... here.[Transcript for "Enemy Of My Enemy" from Fringepedia.net]
AGENT LEE: The Hudson River Valley.
AGENT FARNSWORTH: Right, and this is the map file they accessed the most on Doctor Fayette's hard drive -- the Mohonk Quarry.