Talking about tansan senbei

Cider and carbonated rice crackers were produced using the carbonated water, which was certified as a mineral spring and suitable for drinking. Cider was first produced in Japan in 1901 by utilizing the carbonated spring water of Arima. Cider was produced in Arima until Taisho 15 (1926), but is no longer manufactured there.
Shigematsu Mitsu, the founder of Mitsumori Honpo, was instructed by Koreyoshi Ogata (the second son of Koan Ogata, who founded Tekijuku, a school for Dutch studies, during the Edo period; he loved the natural beauty of Arima Onsen and stayed in Arima frequently) and Jiro Kazahaya (owner of the hot spring inn Hyoe Koyokaku) to make rice crackers using carbonated water around 1907. However, the baking process did not go smoothly. With the advice of Yoshibe Yoshida (owner of Yoshitakaya), he succeeded in baking a thin rice cracker. The ingredients of tansan senbei are wheat flour, potato starch, sugar, and salt, and these were kneaded with carbonated water and baked thinly, making it a gentle food for the stomach. When it was first produced, it was adopted at Dr. Ogata's hospital and other places as a food for weaning babies and the elderly after illness, and was well received.
It would later become a specialty item of Arima Onsen, and according to the Arima Gunshi, a book on the history of Arima, the tansan senbei was made from carbonated water and flavored with several nourishing ingredients, making it a suitable souvenir with a light flavor and rich nourishment.