Whether you’re a top-level CEO looking for advice from the greats or a first-time entrepreneur seeking motivation and inspiration, here are six iconic figures and some of their best business advice.

Alexander Hamilton

“My ambition is prevalent, so that I condemn the groveling condition of a clerk or the like, to which my fortune condemns me, and would willingly risk my life, though not my character, to exalt my station … I mean to prepare the way for futurity.”

— Alexander Hamilton in a 1769 letter

Alexander Hamilton Hamilton was born poor on an island in the Caribbean, and he wrote this letter at age 12, dreaming of something bigger for himself and his career. By 17, when a hurricane devastated his home, the orphan — who was then working as a clerk — wrote an account of the disaster in the local newspaper. Hamilton visualized himself prepare the way for futurity, and that type of steely resolve is invaluable in any venture.

Benjamin Franklin

“[I] retain[ed] only the habit of expressing myself in terms of modest diffidence, never using, when I advanced anything that may possibly be disputed, the words ‘certainly,’ ‘undoubtedly’ or any others that give the air of positiveness to an opinion; but rather say, ‘I conceive or apprehend a thing to be so and so’; ‘it appears to me,’ or ‘I should think it so and so, for such and such reasons’; or ‘I imagine it to be so’; or ‘it is so, if I am not mistaken.’ This habit, I believe, has been of great advantage to me.”

— Benjamin Franklin in his 1789 autobiography

Franklin, one of the country’s founding fathers and author of The Way to Wealth, was also an esteemed inventor, as he’s widely regarded as the father of electricity. He attributes much of his success to the fact that he was always a voracious reader, so hungry for knowledge that he would often stay up with new books late into the night. Speaking with caveats is widely seen as a sign of intelligence, as few things in life are truly certain.

Andrew Carnegie

“We assemble thousands of operatives in the factory, and in the mine, of whom the employer can know little or nothing and to whom he is little better than a myth. All intercourse between them is at an end. Rigid castes are formed, and, as usual, mutual ignorance breeds mutual distrust. Each caste is without sympathy with the other and ready to credit anything disparaging in regard to it … Often there is friction between the employer and the employed, between capital and labor, between rich and poor.”

— Andrew Carnegie in his 1889 book

In The Gospel of Wealth, Carnegie laid out why he would be donating the bulk of his earnings — about $350 million in 1889 dollars — to universities, libraries and other organizations.

John D. Rockefeller

“Criticism which is deliberate, sober and fair is always valuable, and it should be welcomed by all who desire progress. I have had at least my full share of adverse criticism, but I can truly say that it has not embittered me nor left me with any harsh feeling against a living soul. Nor do I wish to be critical of those whose conscientious judgment, frankly expressed, differs from my own. No matter how noisy the pessimists may be, we know that the world is getting better steadily and rapidly, and that is a good thing to remember in our moments of depression or humiliation.”

— John D. Rockefeller in his 1909 book

Rockefeller was an oil magnate, prominent businessman and philanthropist, and one lasting part of his legacy was his status as one of the wealthiest men in history and America’s first billionaire. He took measured criticism into account and used it to propel himself towards his goals, but he strived never to let “adverse criticism” drain him of his time or energy. But Rockefeller didn’t build his legendary Standard Oil worrying about naysayers.

Madam C.J. Walker

“I am a woman that came from the cotton fields of the south. I was promoted from there to the washtub. Then I was promoted to the cook kitchen, and from there I promoted myself into the business of manufacturing hair goods and preparations … I have built my own factory on my own ground.”

— Madam C.J. Walker in a 1912 speech

The girls and women of our race must not be afraid to take hold of business endeavor and, by patient industry, close economy, determined effort and close application to business, wring success out of a number of business opportunities that lies at their very doors, she said in the same speech.

Henry Ford

“Power and machinery, money and goods, are useful only as they set us free to live. They are but means to an end. For instance, I do not consider the machines which bear my name simply as machines. If that was all there was to it I would do something else. I take them as concrete evidence of the working out of a theory of business which I hope is something more than a theory of business — a theory that looks toward making this world a better place in which to live.”

— Henry Ford in his 1922 book

He felt similarly about business in general — that any venture should ultimately be about making the world a better place in which to live. Adopting that very value could help propel the long-term success of any business leader. Ford was a business magnet, mass production innovator and founder of Ford Motor Company.