We switched from an elastic strap to a buckle. We thought the buckle would be a more intentional action. We didn't want the user to accidentally trigger the smell release, since it would take some time for the smell to dissipate.

Instead of two buttons, we switched to one button that confirms the recipe decision. To preview the recipe, the user places the buckle in place.

We needed the buckle to consistently fasten in the same place, so that they would reliably contact the resistors. We ultimately used magnets, placing them in the book pages and sewing them into our buckle. 

Aesthetically, we didn't want the magnets to get in the way of the pages. We experimented with flat washers, but ultimately decided to group the book's pages by 30, so that we could embed the magnets in between pages.