He was familiar with natural drugs and had such profound knowledge that astonished even drug specialists, and according to a theory, it is also said that he mixed drug materials by himself and that he cured a disease of Iemitsu, his grandson.
また生薬にも精通し、その知識は専門家が舌を巻くほどのもので一説には自分で調合していたとも、孫の家光の大病を治したとも言われるほどである。