Dale Steyn sent Pakistan crashing to a new low as South Africa took control on the second day of the first Test at the Wanderers Stadium on Saturday.
Steyn took six for eight in 8.1 overs as Pakistan were shot out for 49, four fewer than their previous lowest total of 53 against Australia in Sharjah in 2002-03.
South Africa led by 204 runs on the first innings but decided not to enforce the follow on.
The hosts were 207 for three in their second innings at the close, an overall lead of 411, with Graeme Smith (52), Hashim Amla (50 not out) and AB de Villiers (63 not out) hitting half-centuries.
It was another triumph for South Africa's barrage of fast bowlers and the third time in less than two seasons that the world's number one Test team had bowled out opponents for less than 50.
Australia were routed out for 47 in 2011/12 and New Zealand were dismissed for 45 earlier this season. Both matches were in Cape Town.
AB de Villiers equalled the South African wicket-keeping record by holding six catches and there were three catches in the slips as the Pakistan batsmen failed to cope with top quality bowling on a pitch with steep and sometimes variable bounce as well as some sideways movement.
Vernon Philander took two for 16 and Jacques Kallis two for 11.
Azhar Ali (13) and captain Misbahul Haq (12) were the only Pakistan batsmen to reach double figures.
Steyn was outstanding, bowling at high pace and making the ball move away disconcertingly from the right-handed batsmen. He started Pakistan's collapse by taking three wickets in 14 balls at the start of the day and followed up with three more in 12 deliveries to wrap up the innings soon after lunch.
Steyn struck with his fifth ball of the day after Pakistan resumed at six for no wicket, having Mohammad Hafeez caught behind for six, edging an out-swinger.
In his next over Steyn trapped new cap Nasir Jamshed leg before wicket when the left-hander went back on his stumps against a full delivery.
Five balls later Steyn claimed the key wicket of Younis Khan, caught at first slip when he edged a perfect out-swinger.
Azhar Ali and Misbah survived for more than an hour before Kallis claimed two wickets in three balls, having both batsmen caught behind.
Batting conditions remained difficult at the start of South Africa's second innings but Graeme Smith and Alviro Petersen put on 82 for the first wicket.