Lithium chloride drops, 250mcg per drop, 600 drops per bottle
Lithium is a vital mineral for mental health (depression, anxiety, aggression, mania, psychosis, dementia, Alzheimers, all can be helped by lithium), but too much can be dangerous. Microdosing lithium (up to 1mg daily) is very safe, and helps many conditions.
One very dangerous interaction with higher lithium doses is with psychedelics. It is not known what the safe level of lithium is with psychedelics, but you should be safe taking up to 1mg daily, since many places have that much already in their water supply.