Former President George H.W. Bush paid tribute to his late wife, former first lady Barbara Bush, in a very simple way at her private funeral in Houston on Saturday: he wore socks with books on them, to honor her commitment to family literacy.

Jim McGrath, the spokesperson for the former president's post-White House years, tweeted out a picture of the socks Saturday. The funeral service, which hundreds attended, paid tribute to her life, and their 73-year-marriage. She died at the age of 92 on Tuesday.

To honor his wife of 73 years and her commitment to family literacy, for which she raised over $110 million over the course of over 30 years, @GeorgeHWBush will be wearing a pair of socks festooned with books at today’s funeral service for former First Lady Barbara Bush. — Jim McGrath (@jgm41) April 21, 2018

The socks worn by the 41st President of the United States of America at today’s funeral for former First Lady Barbara Bush. pic.twitter.com/12libHt1Jv — Jim McGrath (@jgm41) April 21, 2018

The late former first lady dedicated many years of her life to promoting literacy, which she saw as a gateway to opportunities and a future. During her husband's time as vice president and later as president, she honed in on literacy as her signature cause, particularly focusing on awareness for early childhood education and literacy for parents. That belief that every man, woman and child should be able to improve their lives through literacy led to the founding of the Barbara Bush Foundation for Family Literacy in March of 1989. Her daughter Dorothy "Doro" Bush Koch, is the foundation's honorary chair.

Get Breaking News Delivered to Your Inbox

"The American dream is about equal opportunity for everyone who works hard. If we don't give everyone the ability to simply read and write, then we aren't giving everyone an equal chance to succeed," the former first lady once said.

On Saturday, family members also shared the love story of the former president and former first lady, who met when she was 16 and he was 17. That loving home was passed on to their children.

"Their love was a constant in our lives," former Florida governor and presidential candidate Jeb Bush said Saturday of his parents.