Experts say the drowsiness many of us feel during the day may not be because we had too little sleep at night, but because we need an early afternoon nap. Humans were made to sleep not once, but twice, and a 10-minute nap after lunch will make most of us feel better.
In the sentence
Humans were made to sleep not once, but twice.
the phrase "to sleep not once, but twice" seems to mean not a purpose but a manner so that the sentence can be paraphrased as follows:
Humans were so made that they should sleep not once, but twice.
But, I haven't seen a to-infinitival adverbial clause expressing a manner like this before. Is this use of a to-infinitival clause usual? If so, could you give me some examples?