Simplify the following text for a Grade 8 native English-speaking person.
Original: According to tradition , a Dakini gave a black hat to the third Karmapa , Rangjung Dorje ( 1284 â `` 1339 ) , when he was three years old . , The Black Crown became the emblem of the oldest reincarnating Tibetan lineage .
Simplified: Tibetan Buddhists believe that a Dakini gave a black hat to the third Karmapa , Rangjung Dorje ( 1284 - 1339 ) , when he was three years old . The Black Crown became the emblem of this Tibetan lineage known as the Karma Kagyu .