Canis Minor's brightest star, Procyon, rises just ahead of Sirius and gave the constellation its name, before the dog. A second, invisible star travelling with it was worked out mathematically decades before anyone actually saw it.
In 1844 the German astronomer Friedrich Bessel noticed that Procyon's motion across the sky was not perfectly straight but wobbled slightly, as if something unseen were tugging on it, and used the same method that same year to predict an unseen companion for Sirius as well. A faint white dwarf companion, Procyon B, was eventually observed directly by American astronomer John Schaeberle at Lick Observatory in 1896, more than fifty years after Bessel's prediction, confirming that the wobble was real and that a dead, collapsed star was orbiting close beside the brighter one visible to the naked eye.
The delay between prediction and observation is itself part of the story: Bessel worked entirely from small, precise position measurements taken over years, without ever seeing the object his mathematics required to exist, and the confirming telescope had to be considerably more capable than anything available when he made the prediction.
Sirius's own companion followed the identical pattern and was found first, in 1862, but Procyon's case shows the method was not a one-off: the same reasoning applied to two different stars produced two correct, unseen predictions.