A Tidbit from a few days ago covered the long period during which fumbles, blocked kicks, and other balls remained live after going out of bounds. Today's Tidbit covers the four years when incomplete passes that touched a player while in the air were similarly ruled to be live balls, resulting in similar crazy scrambles for the ball.
Football was in crisis following the 1905 season, and they made numerous rule changes to open the game and make it safer. The rule makers had a lot to deal with and only so much time to agree on the new rules, so the early forward-passing rules did not get the attention they deserved. In addition, the rule makers struggled to envision which rules were required since they could not foresee what the game would look like after legalizing the forward pass. The result was a limited set of rules governing the forward pass.
Here are shorthand versions of the passing rules for 1906:
The offense can throw one forward pass per play, and only players behind the line of scrimmage at the snap can throw a forward pass.
Incomplete passes and passes thrown by linemen result in turnovers (spotted at the location of the pass).
Passes touched by ineligible receivers are turnovers (spot foul).
Passes thrown from a spot within five yards left or right of the center are turnovers (spot foul).
Forward passes thrown by the defense are illegal (spot foul).
Passes crossing the goal line without touching a player on either side, whether on the fly or bounding, are illegal and result in a touchback.
That was the entirety of the rules covering the passing game. Missing from the rules was any discussion of pass interference. Pass interference arrived in 1908, but not in the form you might think.