Heft (?), n. Same as Haft, n. [Obs.] Waller.
[1913 Webster]

Heft (?), n.; G. pl. Hefte (#). [G.] A number of sheets of paper fastened together, as for a notebook; also, a part of a serial publication.

The size of “hefts” will depend on the material requiring attention, and the annual volume is to cost about 15 marks. The Nation.
[Webster 1913 Suppl.]