What is the date of the episode that is before 307, run time equals 5:48 and has P.T. Barnum as the topic?
CREATE TABLE "season_3" (
  "episode_number" real,
  "title" text,
  "podcast_date" text,
  "run_time" text,
  "historical_references" text
);
SELECT "podcast_date" FROM "season_3" WHERE "episode_number"<307 AND "historical_references"='p.t. barnum' AND "run_time"='5:48';