As his health deteriorated in these circumstances, Sigüenza prepared for the eventuality of his death, which came in 1700. A scientist to the end, he requested that his body be autopsied, so that physicians could determine what had afflicted him. He explicitly laid out the reasons and concerned that this radical step might be opposed on religious or other grounds by his relatives, he said "I ask in God's name that this be done for the common good, and I command my heir not to interfere, for it matters little that this be done to a body which, within a few days, must be corruption and decay." The autopsy revealed a kidney stone the size of a peach.