I've been listening to Henry Fillmore's "Trombone Family". It brought me to thinking, how long have trombone smears been around in written sheet music? Was Fillmore, a.k.a. "Father of the Trombone Smear", the first to use trombone smears or the first to popularize them? Who was the first to put them into written sheet music if he wasn't?
I'm not sure if anyone has actually pinned down the date or composer. Searches on Google or Trombone History books don't yield very much. According to a quote from one link I found:
Its first deliberate use in performance is fairly recent in the long history of the trombone, and its acceptance as a legitimate technique came somewhat later.
Daniel Speer provides the earliest reference to the glissando I have found (1687), when he wrote, “Some slur the trombone’s sound with the breath, but it comes out better and livelier when it is cleanly articulated with the tongue.”
Take a longer look at the link. It really contains a lot more detail.