Lewis & Short

lĭtūrārĭus, a, um, adj. [litura], of or for rubbing out.
Only as subst.: * lĭtū-rārii, ōrum, m. (sc. libri), books kept for the first rough drafts of writings, blotters (so called from the erasures made in them), Aus. praef. Idyll. 13.