Step 1: Understanding the Concept:
The sale of substances identified as "poisons" is regulated by the Poisons Act, 1919, to prevent accidental or intentional (suicidal/homicidal) poisoning.
Step 2: Detailed Explanation:
1. Record Keeping: Every person authorized to sell poisons must maintain a "Poison Register."
2. Mandatory Entry: At the time of sale, the seller must record the name of the poison, the quantity sold, the purpose of use, the date of sale, and the name, address, and signature of the purchaser.
3. Goal: This creates a paper trail that can be used by law enforcement or forensic experts if the poison is misused.
Step 3: Final Answer:
The legal requirement for the retail sale of poisons is the meticulous recording of each transaction in a dedicated poison register.