Even the humble T21 had one back in the '60s- CISTRS
Controls - waggle about and check they move the right flappy bits in the right direction
Instruments (there were only three) - check altitude reads zero
Straps - done up
Trim - check weight of occupants to see if ballast was required
Release - check yellow wooden knob works the release
Spoilers - check red knob moves them up and down - not that they actually did anything