A shogun is struggling for drinking water!
A panel painting titled Osonoi Legend, a cultural property designated by Suginami Ward and owned by Igusa-hachimangu shrine in NISHIOGI; this painting is now exhibited at the Annex to the Suginami Historical Museum.
Legend has it that in 1189, Minamoto-no-Yoritomo, the first shogun of the Kamakura shogunate, stayed in Igusa (presently, Zenpukuji Park area) on the way to Oushu at that time (Tohoku region now) to conquer the Fujiwara Clan. Then, he attempted to get drinking water by digging the ground with the end of his bow. He finally accomplished his purpose at the seventh attempt. This slow welling of water led to name the area Osonoi (literally, slow well).
Osonoi was restored as waterfalls called Osonoi-no-taki, and they are now headwaters of the ponds in Zenpukuji Park.
飲み水を求めて
将軍が飲み水を求めて苦闘しています！
西荻の井草八幡宮所蔵の、杉並区指定文化財の板絵（「遅の井伝説図」、現在、杉並区立郷土博物館・分館にて展示中）。
伝説によれば、文治5年（1189）、源頼朝（鎌倉幕府初代将軍）が奥州藤原氏の征伐に向かう途中、井草の地（現在の善福寺公園地区）に宿陣。その時、飲み水を得るため、頼朝自ら弓の本筈（もとはず）で地面を掘ったところ、七か所目でようやく水が湧き出たという。そこで、湧出が遅い、として「遅の井」の地名がついたといわれる。
現在、遅の井は「遅野井の滝」として復元され、善福寺公園内の池の源流となっています。
