I can think of no better definition of mysticism than that I found in a comment by Anna Nimm on a website called Materialism, Mysticism and Art
I think of mysticism as direct knowledge of god, whether a personal or a pantheistic god synonymous with nature or a Dionysian life force. And it’s a form of union that is ecstatic, it transports one both beyond the self and also beyond concepts and words; it is a form of knowledge felt by the heart and body (or soul) rather than by the rational mind.
From “Mysticism – experience over intellect”, Follower Anthony Garner’s WELTANSCHUANG blog.
“…most beautiful and profound emotion we can experience is the sensation of the mystical. It is the sower of all true science. To know that what is impenetrable to us really exists, manifesting itself as the highest wisdom and most radiant beauty – which our dull faculties can comprehend only in their primitive form – this knowledge, this feeling, is at the center of all religion.” Albert Einstein
I doubt there are many modern scientists who would agree, sadly. Arrogance and know it all-ness seems to rule.