Separately, Prime Minister Lee Hsien Loong and President Tony Tan Keng Yam visited the tribute site near the Istana's main gates yesterday afternoon, to peruse the condolence messages left by Singaporeans.
They also spoke to the people queueing to pay tribute to Mr Lee Kuan Yew.
By 9pm yesterday, 21,000 messages had been placed there during the day, and there were 3,200 more outside the gates of Parliament.
PM Lee, accompanied by his wife Ho Ching, spent about 10 minutes looking at the messages, cards and flowers.
He shook hands with some of the well-wishers, who expressed their sorrow at his father's death.
A few called out in his direction: "Be strong, Mr Lee."
He replied: "Thank you."
Madam Hiap Cheng Lay, 71, who shook his hand, told The Straits Times later: "When I saw him, all the feelings about Mr Lee Kuan Yew just welled up and I couldn't speak."
Madam Hiap, who sells drinks at a hawker centre, had arrived at the Istana at 11am to lay flowers and waited three hours to see PM Lee after she heard he would be at the tribute site.
President Tan, who came earlier, spoke to security guard Low Kok Wai, among others.
The 54-year-old, who had travelled more than an hour by bus from Boon Lay, said: "I told the President that without Mr Lee Kuan Yew, we wouldn't be enjoying the high standard of living that we have today."
Dr Tan later updated his Facebook page with photos of his lunchtime visit.
People from all walks of life, including foreigners, continued to pay tribute to Mr Lee, who died on Monday.
Some recalled their personal encounters with Singapore's first Prime Minister.
Mrs Jenny Fleming, 57, brought a photograph taken on a flight to the Maldives in 1991 that shows herself with Mr Lee Kuan Yew and his late wife, Madam Kwa Geok Choo.
The former Singapore Airlines flight attendant said Mr Lee had no airs and she joked with him like she did with any other passenger.
He had asked for warm beer, she recalled.
"I replied, 'We don't have warm beer but maybe I could send the chief steward to 7 Eleven to buy a can.' He cracked up.
"I'm nobody but he could laugh along with me. It was just such an honour being able to serve him, to be so close to him."
Retiree Woo Sing Yuen's interaction with Mr Lee was at age five. He was accompanying his hawker father, who was plying the streets with a pushcart carrying dim sum and char kway teow.
They had run into Mr Lee in Chinatown.
Mr Woo recalled being asked: "Are you a good Singaporean?"
And he replied: "Yes, sir."
That commitment to Mr Lee has been a driving force in his life, said Mr Woo, who was a regular blood donor and at age 63, is still a marathon runner.