I never went into the woods without a bare minimum: whistle, little metal mirror, waterproof container of waterproof matches and compass. They weigh next to nothing. All my hiking recent years is in parks surrounding the SF Bay Area which are pretty tame compared to the Sierras, Wind Rivers, or Gros Ventre, so it’s lots,of water and some snacks.
Don’t need to use a mirror: carry a CD instead.