(I admit three games in one day is not a record (see below), but I think it is interesting, nonetheless.)
Doc Reisling pitched 50 innings for Brooklyn in 1904-05 and 250 for Washington in 1909-10. That was it for his MLB experience. Nothing noteworthy is evident in his record. He then became a manager in the minor leagues.
In those days, league championships were decided by winning percentage at the calendar end of the season, not most wins after all games were played. With rainouts common and travel difficult, teams often ended the season with widely different numbers of games played.
In a close pennant race, each contending team's manager would have to decide how aggressive to be in rescheduling previously rained out games, particularly when the opponent was readily available. On the last day of the season, whether it was deemed advisable to play two games or not could depend on the manager's assessment of his team's best path to the championship. Further, an enterprising (and desperate) manager could "game" the situation and decide to play more than two. That's right, more than two!
And so it came to pass in 1914 . . . Doc Reisling decides his team needs three victories on the last day of the season to win the Canadian League championship. And so, a tripleheader was played, which Doc's team swept. Unfortunately for Doc, he had failed to get approval in advance from the League president, who disallowed the third game, which was mooted anyway when Shag Shaughessy (realized the game could only cost his team should they lose and) prevailed on the umpire to call his team's final game midway through because "it was too cold", even though the temperature hadn't changed all day.
(More about tripleheaders,if you are still interested: it turns out that Reisling was not the first to pack the final day. Tripleheaders figured into the NL titles of 1890 and 1896. Minor League pennant races had seen quadrupleheaders, topped off by the rabidly-contested New England League pennant race of 1899. That race produced the sweep of a sextupleheader, which would have edged the other contender's sweep of a tripleheader had a league executive not limited each team to one win only.
As recently as 1920 in the National League, a tripleheader was staged to decide who would take home the share of World Series money allotted in those years to the club finishing third in the standings. Three games were not needed however, as one team clinched third money by winning the first game.)
I can definitely see the announcement of a Sextupleheader drawing a crowd.
https://www.net54baseball.com/attach...1&d=1592246657