nixpkgs.nix (4 lines of code) (raw):

import (fetchTarball { url = "https://github.com/NixOS/nixpkgs/archive/refs/tags/24.05.tar.gz"; sha256 = "sha256:1lr1h35prqkd1mkmzriwlpvxcb34kmhc9dnr48gkm8hh089hifmx"; })