The stopped watch

An original fiction passage set in the nineteenth century.

At the back of the narrow shop, Mr Pryce opened the case of the stopped watch. The customer explained that it had belonged to his father, but the clockmaker did not look up. He held the mechanism close to the lamp and listened. Then, as gently as a man lifting a moth from a windowpane, he tested each wheel. At last, one spring stirred beneath his tool, and the watch gave a faint, regular tick.

Identify the phrase that compares Mr Pryce’s handling of the watch to the careful handling of a fragile creature.