The closest I could find in Ancestry.com census records is this fellow, doubt he is your man:

1860 United States Federal Census about H Siest
Name: H Siest
Age in 1860: 25
Birth Year: abt 1835
Birthplace: Germany, Hessen
Home in 1860: Allegheny Ward 4, Allegheny, Pennsylvania
Gender: Male
Post Office: Allegheny City
Household Members:
Name Age
H Siest 25 Saddler
W Siest 3
C Siest 27
S Siest 1
C Braning 29 Miller
G Hestle 15 App. to Saddley