Why is salt often refereed to as "the refrigerator of the ancient world?"

Identify the type of source based on the information provided. a historian found a journal belonging to an ancient indian princess. the princess liked to keep a record of all the royal women of her dynasty who lived before her time. she tried to collect as much accurate information about their history as possible. her journal is a great source of historical information. based on the passage, the princess’s diary is source.