Two recent books document the potential of altered traits, and states:
The end of my experiementation came after touching on similar altered states during zen sesshins beginning in mid 1970s. Both the meditational and the psychelic experiences were brief, unsustainable and difficult. Zen practice however seemed to offered a progressive path. (Before Zen I had briefly tried encounter groups, Transcendent Meditation, Silva Mind Control, Tibetan Buddhism, etc.; all seemed to promise less and require more than Zen.)
Zen is described as a "religion before religion"; many people who practice other religions also practice Zazen. Nevertheless one is invited at some later stage in practice to have a "general housekeeping of your mind", to take everthing out, examine it, and put helpful things back. Believing in a particular theology and practicing certain rituals are not necessary. Zazen is instead objectless meditation, yet it reaches to all aspects of one's life, possibly through transcendental glimpses of Truth or Source that are typically brief experiences that deeply affect one's subsequent life. Or it can be rationalized as simply seeing beyond normal rational consciousnes and the delusion of Self (ego).
Buddhism identifies three "marks of human existance", i.e., change, suffering, and no-self. Careful reflection can free you from the delusion of a permanent, abiding Self; nevertheless most of us still live within that delusion. The permanent Self delusion is well understood and documented, an ancient heritage stemming from evolution. Kahneman's book, "Thinking, Fast and Slow", documents myriad similar delusions and related irrational tendencies in our "rational" consciousness.
My practice of zazen has continued since the early 1970s for almost 50 years, including daily meditations and seasonal week-long retreats (sesshins), for perhaps a cummulative total of between 20,000 and 30,000 hours of zazen. I am aware of many improvements in my "traits", hopefully reflecting Buddhism's "four immeasurable minds", i.e., kindness, compassion, sympathetic joy, and equanimity. I see these mostly in my changing attitudes toward my past (abysmal) aspirations, views and behaviour, and also in my awareness of the many hisorical, emotional and physical influences on behavior and reasoning, both in myself and in others. Within Zen our objective is just to "see things as they are, and let them go as they go" moment by moment, maintaining our practice forever. And to live fully, responding appropriately to each situation in each moment.