According to "Engishiki" (codes and procedures on national rites and prayers), the area of Emperor Jimmu's mausoleum was 1-cho from east to west and 2-cho from south to north ("cho" is a unit for measuring length and is approximately 109 meters), i.e., about 100m X 100m.
『延喜式』によると、神武天皇陵は、平安時代の初め頃には、東西1町、南2町で大体100m×100mの広さであった。