Posh condemned fierce rivals MK Dons to a first league defeat of the season despite having defenders Nathaniel Knight-Percival and Mark Little dismissed by referee Darren Drysdale.
Knight-Percival walked after just seven minutes after appearing to catch Patrick Bamford with a hand to the face, while Little was red-carded with a quarter-of-an-hour remaining for a crude challenge on Dean Lewington.
The second dismissal arrived moments after substitute Izale McLeod had halved Dons' arrears when pouncing from close range, but that was only the breakthrough the visitors could manage as Posh produced a stunning backs-to-the-wall effort to pocket the points.
Ferguson said: "It was a truly fantastic effort from my players. I'm hugely proud of them and they should also be proud of themselves.
"This victory had nothing to do with tactics or individual ability - it was all about pure endeavour and guts to win a game of football.
"I'm not going to speak about the referee as I don't want to deflect any attention from my players.
"All I would say is that it is rare for one team to end up with two red cards and four yellow cards in a derby while the opposition don't pick up any.
"MK Dons turned it into a cup final with their talk in the build-up, but it was just another game for us."
The hosts had hit the front when Lee Tomlin converted from the spot in the 14th minute after a marauding Danny Swanson run had been illegally ended by Shaun Williams.
Dons men Jon Otsemobor and Bamford both fluffed glorious chances before Posh doubled their advantage when top-scorer Britt Assombalonga thumped his eighth goal of the season from a difficult angle in the 33rd minute.
Dons dominated the remainder, but were frequently frustrated by inspired Posh goalkeeper Bobby Olejnik.
The pick of his many super saves arrived when he tipped a long-range blast from George Baldock on to a post and even when Olejnik was beaten, skipper Tommy Rowe was on hand to nick the ball off the head of Bamford as he looked sure to score.