For the Vedic initiation (the Upanayana) the prescribed ages (when to perform the initiation) are given in various scriptures like the Manu Smriti etc. And, the age limits till which the disciples can be initiated are also given.
2.36. In the eighth year after conception, one should perform the initiation (upanayana) of a Brahmana, in the eleventh after conception (that) of a Kshatriya, but in the twelfth that of a Vaisya.
2.38. The (time for the) Savitri (initiation) of a Brahmana does not pass until the completion of the sixteenth year (after conception), of a Kshatriya until the completion of the twenty-second, and of a Vaisya until the completion of the twenty-fourth.
I am looking to know about similar (upper and lower) age limits (if any exist at all) for the Tantric/Agamic initiation.
Can a very old person be initiated as per the Tantras? Similarly at what age a person becomes qualified for a Tantric initiation?