After a serious heart attack in 1944 Carl Jung wrote during his recovery some letters about his experiences. One begins:

‘What happens after death is so unspeakably glorious that our imagination and our feelings do not suffice to from even an approximate conception of it.’

Jung believed at this time that ‘the dissolution of our time-bound form in eternity brings no loss of meaning. Rather does the little finger know itself a member of the hand.’
In a longer letter to Kristine Mann an American analytical psychologist who was terminally ill he wrote of what he experienced during the attack. The longer account is given in his autobiography Memories, Dreams and Reflections. Whilst greatly weakened physically he notes that fortunately his head hadn’t suffered:

‘On the whole my illness proved to be a most valuable experience, which gave me the inestimable opportunity of a glimpse behind the veil … When you can give up the crazy will to live and when you seemingly fall into a bottomless mist, then the truly real life begins with everything you were meant to be and never reached. It is something ineffably grand. I was free, completely free and whole, as I never felt before.’

Jung then describes his near death experience of floating above the earth and seeing it as an immense globe in an inexpressibly beautiful blue light; he sees the southern end of India shining in a bluish silvery light with what was then Ceylon, now Sri Lanka like a shimmering opal in the deep blue sea. He goes on:

‘I was in the universe, where there was a big solitary rock containing a temple. I saw its entrance illuminated by a thousand small flames of coconut oil. I knew I was to enter the temple and I would reach full knowledge.’

At this moment a messenger appears summoning Jung back to the world and the whole vision collapses. However during his recovery in a state alternating between sleep and wakefulness Jung experiences what he calls ‘the complete vision’. He felt in a deep union with somebody or something that was itself united – ‘the mystic Agnus’. The experience was permeated by ‘an incomparable, indescribable feeling of eternal bliss, such as I never could have imagined as being within reach of human experience.’
In the letter Jung says that death is the hardest thing from the outside but once inside ‘you taste of such completeness and peace and fulfilment that you don’t want to return.’ The experience was so overwhelming that as he recovered Jung suffered from black depressions which felt like dying as he returned to ‘this fragmentary, restricted, narrow, almost mechanical life, where you were subject to the laws of gravity and cohesion, imprisoned in a system of 3 dimensions and whirled along with other bodies in the turbulent stream of time. There was fullness, meaning fulfilment, eternal movement (not movement in time).’

Jung finishes by saying that throughout his illness he had felt carried by something and that ‘my feet were not standing on air and I had the proof that I have reached a safe ground.’ He urges Kristine Mann to do whatever she does with sincerity and that this will become the bridge to her wholeness, ‘a good ship that carries you through the darkness of your second birth, which seems to be death to the outside… Be patient and regard it as another difficult task, this time the last one.’