Here is an example:
//below gets the historical sate if an item
var PersistenceExtensions = Java.type("org.openhab.core.persistence.extensions.PersistenceExtensions");
var ZonedDateTime = Java.type("java.time.ZonedDateTime");
var myPersistentItem = ir.getItem("Zigbeesengledbulb_Zigbeesengledbulb");
logger.info("The pyload is {}", myPersistentItem);
var sinceDate = ZonedDateTime.now().minusDays(7);
//var sinceDate = ZonedDateTime.now().minusHours(5);
var maximumValueSince = PersistenceExtensions.maximumSince(myPersistentItem, sinceDate);
logger.info("Historic item is {}", maximumValueSince);
logger.info("Item name is {}", maximumValueSince.name);
logger.info("Item state is {}", maximumValueSince.state);
More examples here: