Why, though, were we told that “The Account of the Merkava should only be taught to the wise and to those able to deduce through wisdom on their own” (Mishna Chagiga 2:1)? Apparently because there were dangers involved, as in the case of the child who studied it and suddenly died (Chagiga 13b) and of the student who was struck with leprosy when studying it (J.T. Chagiga 3:1). Also because the Divine Presence and various ministering angels appear before those who study it (Chagiga 14b), or a fire would surround them and the earth would tremble (J.T. Chagiga 3:1), and few could withstand that.
Ramchal refers to the Merkava later on in Klach as we’ll see  and in other esoteric works to a limited extent. But he dedicated an entire, albeit small, book to the subject entitled Pinot HaMerkava (“The Corners of the Merkava”) .
An abstruse work, Pinot HaMerkava ties various themes together. Most significantly for our purposes it addresses the role that the Merkava plays in prophecy and what the prophet is to “envision”, and the place each “corner” has in the ultimate redemption and revelation of God’s Yichud. It’s thus easy to see why Ramchal discusses the subject at this early juncture even though its particulars don’t quite belong here.
 See Petachim 24, 31, 57, and 129.
 It’s contained in Ginzei Ramchal pp. 310-359.
(c) 2011 Rabbi Yaakov Feldman
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