Father Bernabe Cobo - Inca Religion and Customs – 'Sacrifice'
Type of Spiritual Experience
Cobo never saw any sacrifices take place, as such we can be pretty sure he is taking literally what is a symbolic act.
Sacrifice in all mystic religions is the giving up of an ordinary life, including in some cases sex, in order to dedicate yourself to being a priest [or shaman]. Cobo of all people ought to have had some inkling of what this meant as he had taken vows himself, but I get the impression he was too bigoted to make the connection.
The term sacrifice also has some other connotations which you will be able to see from the link to the symbol section. It would have been a great honour for any child to have been chosen and a time for rejoicing.
Notice the contradictions - on the one hand he says noncompliance was severely punishable and on the other hand he says that very few were ever punished. So one would guess that the first sentence is a lie.
A description of the experience
Inca Religion and Customs – Father Bernabe Cobo [translated by Roland Hamilton]
Although all of the Indian nations of this Kingdom of Peru paid careful attention to their gods and shrines, none of them came anywhere near priding themselves on being as religious as the Incas.
In fact the Incas … observed what was ordained with such care that their practices were inviolable laws and beliefs for them. Offenses committed against these laws or even carelessness in the stipulated forms of worship were severely punishable.
Nevertheless, the Incas were so religious that they say very few were punished for noncompliance, even though great care was taken to keep track of religious observances.
Certainly it was no easy matter to comply. Here is an example: For those selected to sacrifice their child, though this was an only child, it was a major offense to show any signs of sadness; on the contrary they were obliged to do it with gestures of happiness and satisfaction, as if they were taking their children to bestow upon them a very important reward.