וְאַתָּ֨ה בֶן־אָדָ֜ם קַח־לְךָ֣ ׀ חֶ֣רֶב חַדָּ֗ה תַּ֤עַר הַגַּלָּבִים֙ תִּקָּחֶ֣נָּה לָּ֔ךְ וְהַעֲבַרְתָּ֥ עַל־רֹאשְׁךָ֖ וְעַל־זְקָנֶ֑ךָ וְלָקַחְתָּ֥ לְךָ֛ מֹאזְנֵ֥י מִשְׁקָ֖ל וְחִלַּקְתָּֽם׃
And thou, Son of man, take a sharp knife; a barber’s razor take for thyself; and pass it over thy head, and over thy beard: then take balances to weigh, and divide the hair.
"The vestibular system has been a mystery for centuries. Although the anatomy of the discovery of the vestibular apparatus dates to the Renaissance era (c.1400 - c.1600), its function and physiology were a mystery until the middle of the 19th century (Hachmeister, 2003)."
https://canadianaudiologist.ca/a-glimpse-into-the-history-of-vestibular-testing/
וְיֹתֵ֕ר שֶׁהָיָ֥ה קֹהֶ֖לֶת חָכָ֑ם ע֗וֹד לִמַּד־דַּ֙עַת֙ אֶת־הָעָ֔ם וְאִזֵּ֣ן וְחִקֵּ֔ר תִּקֵּ֖ן מְשָׁלִ֥ים הַרְבֵּֽה׃
A further word: Because Koheleth was a sage, he continued to instruct the people. He listened to and tested the soundness of many maxims.
ואזן. שירים או חבור מאזני החכמה או הוא מן אזנים כענין השמיע: