worth one's salt

[T]he encouragement for Shipwrights continues great at the Capital; to which all young People are naturally deſirous to come, whenever they fancy their abilities would diſtinguiſh them, or find a deſire to improve themſelves in their profeſſion; which two claſſes comprehend all the Shipwrights that will ever be worth their salt!

1786, A[lexander] Dalrymple, A Fair State of the Case between the East India Company and the Owners of Ships Now in Their Service. […], London: Printed by George Bigg …; and sold by J. Sewell, […], →OCLC, pages 46–47

Everyone who is worth his salt has his enemies, who must be beaten, be they evil thoughts and habits in himself, or spiritual wickedness in high places, or Russians, or Border-ruffians, or Bill, Tom, or Harry, who will not let him live his life in quiet till he has thrashed them.

1857, [Thomas Hughes], “The Fight”, in Tom Brown’s School Days. […], Cambridge, Cambridgeshire: Macmillan & Co., →OCLC, part II, pages 312–313

It did all our hearts good to see him spit in his hand, knit his brows, and make the blade sing through the air. It was plain from every line of his body that our new hand was worth his salt.

1881–1882, Robert Louis Stevenson, “Narrative Continued by the Doctor: End of the First Day’s Fighting”, in Treasure Island, London; Paris: Cassell & Company, published 14 November 1883, →OCLC, part IV (The Stockade), page 142

Every executive worth his salt has his own private charity, ranging all the way from the Society for the Prevention of Cruelty to Animals to raising money for organizations concerned with better sex education in our public schools.

1966 May, Arnold H. Maremont, “Public Relations—the Tail that Wags the Dog?”, in Michigan Business Review, volume XVIII, number 3, Ann Arbor, Mich.: Graduate School of Business Administration, University of Michigan, →ISSN, →OCLC, page 11, column 1

Surely any "science" worth its salt ought to try to be true to its name and be as objective as it can, make careful measurements, count something.

2000, Ronald W. Maris, Alan L[ee] Berman, Morton M. Silverman [et al.], “The Empirical Foundations of Suicidology”, in Comprehensive Textbook of Suicidology, New York, N.Y.; London: Guilford Press, →ISBN, part I (Foundations of Suicidology), page 62