The Bhagavad Gita by Eknath Easwaran

The Eternal Godhead ╯
at the time of death he will think of nothing else. Otherwise,
in the chaos of death, he will panic and lose his way.
Krishna describes in detail what happens to consciousness
at the moment of death (8:12–13). These verses actually
describe the yogis as being in control of the process of
death. Directing their consciousness step by step through the
difficult ordeal of leaving the body, they attain the supreme
goal. This idea is also accepted by one of the greatest teachers
of meditation in ancient India, Patanjali, who says in the
Yoga Sutras that the yogi dies at will. Similar descriptions of
the death process occur in the Upanishads, though there the
dying person is not necessarily in control. The Upanishads
give a detailed account:
When the Self seems to become weak and sink into unconsciousness,
the vital breaths gather to him. Then he takes
with him those particles of light and descends into the
heart. When the consciousness that is in the eye turns back,
the dying person no longer sees any form. “He is becoming
one,” they say; “he does not see.” “He is becoming one,” they
say; “he does not smell.” “He is becoming one,” they say; “he
does not taste.” “He is becoming one,” they say; “he does
not speak.” “He is becoming one,” they say; “he does not
hear.” “He is becoming one,” they say; “he does not think or
touch or know.” The point of his heart lights up, and by that
light the Self departs, either through the eye, or the skull, or
through some other door of the body. And when he departs,
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