Step 1: Identify the patron of the Ashokan Pillars.
The Lion Capital is the crowning piece of a pillar erected by the Mauryan Emperor Ashoka.
Step 2: Determine the period of Ashoka's reign.
Emperor Ashoka the Great ruled the Mauryan Empire from circa 268 to 232 BCE. This period falls squarely within the 3rd Century BCE. Therefore, the pillar and its capital were carved during this time.