續一切經音義 7.126

7.126

樺皮（上胡罵反木名也皮堪為燭者其中有赤白麁細白細者堪書梵夾以彼土無紙多以貝多葉或多羅葉反樺皮書字也）。

樺皮 (The upper character is pronounced with the fanqie hu + ma; the name of a tree. Its bark can serve as candles; among them are red, white, coarse, and fine varieties. The fine white bark can be used to write Indic pustaka manuscripts, because that land has no paper, so they mostly write on pattra leaves, tāla leaves, or birch bark).