Answer:
"In one hand".
Step-by-step explanation:
A prepositional phrase is one which consists of prepositions and the object which is governed by the same. In the given sentence, the prepositional phrase is ‘in one hand’. This is because ‘in’ is a preposition and it is governing the object rattle which is held in one hand. While singing the snake dance song, the leader is being followed who holds the rattle in one hand portraying the leader and his attributes.