**** From the mid-19th century, it was understood that the possibility of squaring the circle depended upon the nature of π (pi).
」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」」＜第２章　物質の構成粒子＞（教p19-）