Scholars of Elizabethan theatre agree that the stage in Elizabethan playhouses could have a trap door, for example in the Globe Theatre (built in 1699) and the Red Lion. In his study Shakespeare: The Winter's Tale (Penguin, 1988), Christopher Hardman writes (page 95, emphases added):
The stage dimensions are calculated to be forty-three feet wide by approximately twenty-seven feet from back to front, on the evidence of the Fortune, and there was a trap in the stage certainly big enough for two men to go through at the same time.
Hardman does not cite a source for the dimensions of the trap and I could not find any mentions of the width in sources such as Shakespeare Survey 52: Shakespeare and the Globe, Elizabethan Popular Theatre: Plays in Performance by Michael Hattaway or Shakespearean Entrances by M. Ichikawa.
I assume the claim about the width of the trap door would be based either on stage directions that require two persons to disappear simultaneously or descriptions by contemporaries. What is the evidence that would support Christopher Hardman's claim?