The tradition began as a nod to how far society has come since 1557, when Pope Paul IV first established The Index of Prohibited Books to protect Catholics from controversial ideas.

这个传统是为了适应多远社会的到来，因为1557年，教皇保罗四首先建立起“违禁书籍索引”，以防止天主教徒受到有争议的想法之害。

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Some are distinguished by design or material, such as the nearly two pounds of solid gold that King Philip II of Spain attached to his profession of fealty to Pope Paul IV in 1555.

WSJ: Lux in Arcana | Capitoline Museum | The Papacy's Private Papers | By Francis X. Rocca