Na-adjective in attributive form before という?

Question

I have trouble with the last part of the following sentence, starting from the last 私 (bolded):

その読まれる作品は、たいてい私のものと、川添と云う少女のもので、私の作品が、たいていは家庭のことを書いているのに反して、川添と云う少女のは、森の梟{ふくろう}とか幻想の虹{にじ}とかいったハイカラなもので、私はその少女の作品から、「神秘的」なと云う愕{おどろ}くべき上品な言葉を知った。

(I've left the original furigana; source: http://www.aozora.gr.jp/cards/000291/card47785.html )

Is the な in 「神秘的」なと云う the attributive marker for the na-adjective 神秘的? It would make sense but I always thought you had to have a full clause before という (not just the attributive form of a na-adjective). As I understand it, this particular instance seems to be quoting from the girl's repertoire, as if saying "in her own words, she would call it mysterious."

Also, I am a bit confused as to what is being qualified here since 云う, 愕くべき and 上品な are all in their attributive form. I'm reading it as 愕くべき上品 ("a wonderful elegance") and simiarly 「神秘的」なと云う上品 ("one that could be called mysterious"), but please correct me if I'm wrong. (By the way, is there a reason why 云う is not in the continuative form? Both 上品 and 言葉 already have qualifiers in the attributive form so I thought a second qualifier should come in the continuative form.)

Tentative (rough) translation: From her work, I learnt words whose surprising elegance could be called "mysterious."

Thanks!

Answer 1

Obviously that な is a part of the na-adjective 神秘的な. I think this sentence is usually written either as:

「神秘的な」と云う愕くべき上品な言葉を知った。

Or:

「神秘的」と云う愕くべき上品な言葉を知った。

I don't know whether this tricky usage of brackets was intended by the author. But I think the original text is considered strange at least by today's standards.

Here "「神秘的(な)」" is in apposition with 愕くべき上品な言葉 (literally "surprising elegant word"). My translation would be "I learnt this surprisingly elegant word, called mysterious."