I know that it has to be a certain kind. To answer this question we need to take a look at the humble bean. Beans belong to a family of plants called legumes. Legumes are as varied as the clover to the mimosa tree yet they share some basic characteristics. All members of this family produce their seed in a special sack called a pod.
Legumes are very beneficial because they help replace nitrogen in the soil.
In addition, the bean itself is high in nutrients, vitamins such as folic acid, and proteins. In the past, dried beans were often a favorite food of colonial trappers, sailors, or any others who took long voyages. That's because there is no food that is lighter to carry, longer lasting, or contains more protein and nutrients that the bean. In many respects, it was the ideal food for these type of people. In order to cook an effective bean meal, dried beans had to be re-hydrated or softened up.