Sentence:  ‘... the Pope ... had to send him a valuable Gift, which you may see some day.' Nüssler did, one day, see this <WSD>preciosity</WSD>: a Crucifix, ebony bordered with gold, and the Body all of that metal, on the smallest of altars, in Walrave's bedroom. 
Meaning of the word marked with <WSD> tags:  Something of high value or worth.