To safely collect the protective fluid of our nervous system, one must imperatively puncture below the second lumbar vertebra (L2), the area where the main central nerve cord ends.

noli's read

This safety advice is based on an undeniable human anatomical reality validated by science. According to reference anatomy treatises such as Gray's Anatomy (scientific consensus), the main central nervous structure generally ends between the first and second lumbar vertebrae in adults. Clinical safety guidelines (expert opinion and observational imaging data) therefore always recommend aiming for the spaces located lower, between the third and fifth vertebrae. At this lower level, one finds only mobile nerve fibers that naturally move aside, eliminating the risk of touching the main cord. It is a golden rule of bodily protection that does not suffer from any exaggeration.

the sources

No named source held this one up — that absence is part of the verdict.