Captain Daniel Flynn led his troops by example, top-scoring with 41 runs off 73 balls during his 116 minutes at the crease before being caught by Stags wicketkeeper van Wyk off a delivery from Doug Bracewell.
Flynn's haul included six fours.
Scott Kuggeleijn was the next best of the visitors with 36 off 45 balls during 56 minutes of action.
Others to make respectable contributions to the Knights' first innings were Ish Sodhi and Joe Carter, with 29 and 26 runs respectively.
Bracewell took two wickets, including BJ Watling lbw for a duck, for the loss of 52 runs during his 14 overs with the ball. Captain Kieran Noema-Barnett took three wickets for 26 runs during his 14 overs.
Bevan Small also took three wickets while leaking 47 runs during 11.3 overs. The Stags' other successful bowler, Ben Wheeler, took two wickets while conceding 32 runs in 15 overs.
Tarun Nethula was the only Stags bowler not to take a wicket. He leaked 27 runs during his six overs with the ball.
Stags opener Jamie How performed well with the bat and was unlucky to get an lbw call after scoring 35 runs off 56 balls during 72 minutes of action in windy conditions. He hit three fours and one six, while Hay managed five fours.
"Obviously we would have preferred the Knights to finish with 150 or 160 runs but we'll take 190 at the end of the day," Hamilton said.
He was impressed with the Knights' ninth-wicket total of 50 runs over 59 minutes. The Stags' first 50 runs were manufactured during 64 minutes. The Stags took 144 minutes to score 100 runs, two minutes fewer, but in one more over than their visitors required.
In Wellington, Tom Blundell top-scored with 118 during the Firebirds' first innings against the Auckland Aces at the Basin Reserve. Blundell's previous best first-class knock was 32.
James Franklin was another to crack the ton, with 110 not out as the Firebirds finished day one at 337/6.
At the University Oval in Dunedin, the Canterbury Wizards finished their first innings with 280 runs off 85.1 overs. The Otago Volts managed 47/2 off 11 overs before the end of play. Tom Latham was the best of the Wizards with 93.
