In a game I am playing, I ran across the sentence,
"ひらりと白い[欠片]{かけら}がひとひら、舞い込んできた。"
It appears that both 欠片 and ひとひら are nouns. After this, there is no particle before the verb. What type of grammar structure is this?
I found a translation online that suggests that this line means "Nimbly a white fragment like a petal floated down," which makes sense, but I am not sure how the sentence means this.