What is/are the cause/s of becoming "perceiveless", an unconsciouse-being? Althought as most not desired existence sometimes quoted, there seems to be less information about the cause why one gains the existence of an "not-perceiving-being", Unconscious beings (asaññasatta). [explained as "only body 'no' mind" often]

What is the cause, what is the required tendency to gain a asaññasatta-existence, state? Which kind of training should one go after to gain this long lasting state (which causes one to become a "fortuitous-arising-ists" (DN1), or a materialist, when falling from there)

Maybe some experts or googlyanika (those living dependency of teacher google) here are willing to elaborate about the being and coming into being of such beings.

(Note: this is not given for trade, exchange, stacks or entertaining, but as a tiny emergency-question for a timely exit from this wheel nourishing on delusion)
SN 23.2 defines "a being" ("satta") as strong clinging to one or more of the five aggregates. One the meanings of the word "satta" is "clinging". To cling requires a mind. Therefore, it appears there can be no such thing as an unconscious "being".

In my search, I only found the term asaññasattā in AN 9.24 plus the DN and, in the sequence of the teaching, appears related to the 4th jhana. The 4th jhana is obviously not "unconscious". It follows it appears the term "asaññasattā" needs to be examined carefully, for what it really means. The impression is "asaññasattā" means not having any salient perception because the mind only has equanimity as its object. It appears "asaññasattā" does not mean "unconscious". 

Regardless, these types of teachings found in the Anguttara Nikaya &amp; Digha Nikaya are often suspicious and, imo, best ignored.