Why did Justice Peckham compare bakery work with mining work?

In Lochner v. New York, Justice Rufus Peckham compared bakery work to mining work to determine whether the state could legitimately exercise its police power to regulate working hours.1

The Supreme Court had previously upheld maximum-hours laws for dangerous occupations, such as mining, in the case of Holden v. Hardy (1898). By referencing this precedent, Peckham sought to establish a standard for when such government interference is permissible. He argued that the state could only curtail the freedom of contract—a liberty protected by the Fourteenth Amendment—if the regulation was necessary to protect public health or the health of workers in inherently hazardous trades.1

Peckham ultimately concluded that baking was not a dangerous or unhealthful trade comparable to mining. Relying on evidence suggesting that baking did not pose unique health risks, he determined that the law was not a valid health measure and therefore constituted an unconstitutional infringement on the liberty of contract.1