People combined observable treatment with words, gestures, and religious aid. A plant might be used for physical effects, symbolic meaning, or both.
Medieval healing texts survive better than Viking-Age instructions. They place Christian prayers beside older formulae and practical recipes. Continuity is possible but must be evaluated text by text.
Sagas feature curses, love magic, confusion, and bodily harm. As literature, these motifs expose hidden conflict; they reveal social anxieties as well as imagined techniques.
Poisonous plants such as henbane in a grave do not prove deliberately induced trance. Dose, use, and route of deposition are unknown. Modern self-experiment would be dangerous, not historical research.