According to a legend, he was so impressed with the temple's fine spring water, called 'Tokko water', which had been dug by Kobo Daishi using Tokko (a religious tool like a short stick), that he built Gansuiken.
含翆軒は、弘法大師が独鈷を用いて掘られて湧水した名水「独鈷水」があるのを喜んで設けたと伝えられている。